postfix настройка smtp аутентификации

The recipient of undeliverable mail that cannot be returned to
the sender. This feature is enabled with the notify_classes
parameter.

The numerical Postfix SMTP server response code for
an access(5) map “defer” action, including “defer_if_permit”
or “defer_if_reject“. Prior to Postfix 2.6, the response
is hard-coded as “450”.

Do not change this unless you have a complete understanding of RFC 5321.

This feature is available in Postfix 2.6 and later.

The numerical Postfix SMTP server response code for
an access(5) map “reject” action.

Do not change this unless you have a complete understanding of RFC 5321.

The amount of time between verify(8) address verification
database cleanup runs. This feature requires that the database
supports the “delete” and “sequence” operators. Specify a zero
interval to disable database cleanup.

After each database cleanup run, the verify(8) daemon logs the
number of entries that were retained and dropped. A cleanup run is
logged as “partial” when the daemon terminates early after “postfix
reload“, “postfix stop“, or no requests for $max_idle
seconds.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

This feature is available in Postfix 2.7.

Overrides the default_transport parameter setting for address
verification probes.

This feature is available in Postfix 2.1 and later.

Overrides the local_transport parameter setting for address
verification probes.

This feature is available in Postfix 2.1 and later.

Lookup table for persistent address verification status
storage. The table is maintained by the verify(8) service, and
is opened before the process releases privileges.

The lookup table is persistent by default (Postfix 2.7 and later).
Specify an empty table name to keep the information in volatile
memory which is lost after “postfix reload” or “postfix
stop“. This is the default with Postfix version 2.6 and earlier.

Specify a location in a file system that will not fill up. If the
database becomes corrupted, the world comes to an end. To recover,
delete (NOT: truncate) the file and do “postfix reload“.

Postfix daemon processes do not use root privileges when opening
this file (Postfix 2.5 and later). The file must therefore be
stored under a Postfix-owned directory such as the data_directory.
As a migration aid, an attempt to open the file under a non-Postfix
directory is redirected to the Postfix-owned data_directory, and a
warning is logged.

Examples:

address_verify_map = hash:/var/lib/postfix/verify
address_verify_map = btree:/var/lib/postfix/verify

This feature is available in Postfix 2.1 and later.

Enable caching of failed address verification probe results. When
this feature is enabled, the cache may pollute quickly with garbage.
When this feature is disabled, Postfix will generate an address
probe for every lookup.

This feature is available in Postfix 2.1 and later.

The time after which a failed probe expires from the address
verification cache.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.1 and later.

The time after which a failed address verification probe needs to
be refreshed.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

This feature is available in Postfix 2.1 and later.

A safety limit that prevents address verification requests from
overwhelming the Postfix queue. By default, the number of pending
requests is limited to 1/4 of the active queue maximum size
(qmgr_message_active_limit). The queue manager enforces the limit
by tempfailing requests that exceed the limit. This affects only
unknown addresses and inactive addresses that have expired, because
the verify(8) daemon automatically refreshes an active address
before it expires.

This feature is available in Postfix 3.1 and later.

How many times to query the verify(8) service for the completion
of an address verification request in progress.

By default, the Postfix SMTP server polls the verify(8) service
up to three times under non-overload conditions, and only once when
under overload. With Postfix version 2.5 and earlier, the SMTP
server always polls the verify(8) service up to three times by
default.

Specify 1 to implement a crude form of greylisting, that is, always
defer the first delivery request for a new address.

Examples:

# Postfix ≤ 2.6 default
address_verify_poll_count = 3
# Poor man's greylisting
address_verify_poll_count = 1

This feature is available in Postfix 2.1 and later.

The delay between queries for the completion of an address
verification request in progress.

The default polling delay is 3 seconds.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.1 and later.

The time after which a successful probe expires from the address
verification cache.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.1 and later.

The time after which a successful address verification probe needs
to be refreshed. The address verification status is not updated
when the probe fails (optimistic caching).

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.1 and later.

Overrides the relay_transport parameter setting for address
verification probes.

This feature is available in Postfix 2.1 and later.

Overrides the relayhost parameter setting for address verification
probes. This information can be overruled with the transport(5) table.

This feature is available in Postfix 2.1 and later.

The sender address to use in address verification probes; prior
to Postfix 2.5 the default was “postmaster”. To
avoid problems with address probes that are sent in response to
address probes, the Postfix SMTP server excludes the probe sender
address from all SMTPD access blocks.

Specify an empty value (address_verify_sender =) or <> if you want
to use the null sender address. Beware, some sites reject mail from
<>, even though RFCs require that such addresses be accepted.

Examples:

address_verify_sender = <>
address_verify_sender = [email protected]

This feature is available in Postfix 2.1 and later.

Overrides the sender_dependent_default_transport_maps parameter
setting for address verification probes.

This feature is available in Postfix 2.7 and later.

Overrides the sender_dependent_relayhost_maps parameter setting for address
verification probes.

This feature is available in Postfix 2.3 and later.

The time between changes in the time-dependent portion of address
verification probe sender addresses. The time-dependent portion is
appended to the localpart of the address specified with the
address_verify_sender parameter. This feature is ignored when the
probe sender addresses is the null sender, i.e. the address_verify_sender
value is empty or <>.

Historically, the probe sender address was fixed. This has
caused such addresses to end up on spammer mailing lists, and has
resulted in wasted network and processing resources.

To enable time-dependent probe sender addresses, specify a
non-zero time value. Specify a value of at least several hours,
to avoid problems with senders that use greylisting. Avoid nice
TTL values, to make the result less predictable.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.9 and later.

The name of the verify(8) address verification service. This service
maintains the status of sender and/or recipient address verification
probes, and generates probes on request by other Postfix processes.

Overrides the transport_maps parameter setting for address verification
probes.

This feature is available in Postfix 2.1 and later.

Overrides the virtual_transport parameter setting for address
verification probes.

This feature is available in Postfix 2.1 and later.

The alias databases for local(8) delivery that are updated with
“newaliases” or with “sendmail -bi“.

This is a separate configuration parameter because not all the
tables specified with $alias_maps have to be local files.

Examples:

alias_database = hash:/etc/aliases
alias_database = hash:/etc/mail/aliases

The alias databases that are used for local(8) delivery. See
aliases(5) for syntax details.
Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.
Note: these lookups are recursive.

The default list is system dependent. On systems with NIS, the
default is to search the local alias database, then the NIS alias
database.

If you change the alias database, run “postalias /etc/aliases”
(or wherever your system stores the mail alias file), or simply
run “newaliases” to build the necessary DBM or DB file.

The local(8) delivery agent disallows regular expression substitution
of $1 etc. in alias_maps, because that would open a security hole.

The local(8) delivery agent will silently ignore requests to use
the proxymap(8) server within alias_maps. Instead it will open the
table directly. Before Postfix version 2.2, the local(8) delivery
agent will terminate with a fatal error.

Examples:

alias_maps = hash:/etc/aliases, nis:mail.aliases
alias_maps = hash:/etc/aliases

Restrict local(8) mail delivery to external commands. The default
is to disallow delivery to “|command” in :include: files (see
aliases(5) for the text that defines this terminology).

Specify zero or more of: alias, forward or include,
in order to allow commands in aliases(5), .forward files or in
:include: files, respectively.

Example:

allow_mail_to_commands = alias,forward,include

Restrict local(8) mail delivery to external files. The default is
to disallow “/file/name” destinations in :include: files (see
aliases(5) for the text that defines this terminology).

Specify zero or more of: alias, forward or include,
in order to allow “/file/name” destinations in aliases(5), .forward
files and in :include: files, respectively.

Example:

allow_mail_to_files = alias,forward,include

Allow a sender or recipient address to have `-‘ as the first
character. By
default, this is not allowed, to avoid accidents with software that
passes email addresses via the command line. Such software
would not be able to distinguish a malicious address from a
bona fide command-line option. Although this can be prevented by
inserting a “–” option terminator into the command line, this is
difficult to enforce consistently and globally.

As of Postfix version 2.5, this feature is implemented by
trivial-rewrite(8). With earlier versions this feature was implemented
by qmgr(8) and was limited to recipient addresses only.

Enable the rewriting of the form “user%domain” to “user@domain”.
This is enabled by default.

Note: as of Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true:

To get the behavior before Postfix version 2.2, specify
“local_header_rewrite_clients = static:all”.

Example:

allow_percent_hack = no

Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
from untrusted clients to destinations matching $relay_domains.

By default, this feature is turned off. This closes a nasty open
relay loophole where a backup MX host can be tricked into forwarding
junk mail to a primary MX host which then spams it out to the world.

This parameter also controls if non-local addresses with sender-specified
routing can match Postfix access tables. By default, such addresses
cannot match Postfix access tables, because the address is ambiguous.

A list of non-default Postfix configuration directories that may
be specified with “-c config_directory” on the command line (in the
case of sendmail(1), with the “-C” option), or via the MAIL_CONFIG
environment parameter.

This list must be specified in the default Postfix main.cf file,
and will be used by set-gid Postfix commands such as postqueue(1)
and postdrop(1).

Specify absolute pathnames, separated by comma or space. Note: $name
expansion is not supported.

Always add (Resent-) From:, To:, Date: or Message-ID: headers
when not present. Postfix 2.6 and later add these headers only
when clients match the local_header_rewrite_clients parameter
setting. Earlier Postfix versions always add these headers; this
may break DKIM signatures that cover non-existent headers.
The undisclosed_recipients_header parameter setting determines
whether a To: header will be added.

Optional address that receives a “blind carbon copy” of each message
that is received by the Postfix mail system.

Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements RFC 3461.

Note: with Postfix 2.2 and earlier the sender will be notified
when the BCC address is undeliverable.

Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself.

The time unit over which client connection rates and other rates
are calculated.

This feature is implemented by the anvil(8) service which is available
in Postfix version 2.2 and later.

The default interval is relatively short. Because of the high
frequency of updates, the anvil(8) server uses volatile memory
only. Thus, information is lost whenever the process terminates.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

How frequently the anvil(8) connection and rate limiting server
logs peak usage information.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.2 and later.

With locally submitted mail, append the string “@$myorigin” to mail
addresses without domain information. With remotely submitted mail,
append the string “@$remote_header_rewrite_domain” instead.

Note 1: this feature is enabled by default and must not be turned off.
Postfix does not support domain-less addresses.

Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true:

To get the behavior before Postfix version 2.2, specify
“local_header_rewrite_clients = static:all”.

With locally submitted mail, append the string “.$mydomain” to
addresses that have no “.domain” information. With remotely submitted
mail, append the string “.$remote_header_rewrite_domain”
instead.

Note 1: this feature is enabled by default. If disabled, users will not be
able to send mail to “user@partialdomainname” but will have to
specify full domain names instead.

Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true:

To get the behavior before Postfix version 2.2, specify
“local_header_rewrite_clients = static:all”.

How long the postkick(1) command waits for a request to enter the
Postfix daemon process input buffer before giving up.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.1 and later.

List of users who are authorized to flush the queue.

By default, all users are allowed to flush the queue. Access is
always granted if the invoking user is the super-user or the
$mail_owner user. Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list. The username
“unknown” is used for processes whose real UID is not found in the
password file.

Specify a list of user names, “/file/name” or “type:table” patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A “/file/name”
pattern is replaced
by its contents; a “type:table” lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify “!pattern”
to exclude a name from the list. The form “!/file/name” is supported
only in Postfix version 2.4 and later.

This feature is available in Postfix 2.2 and later.

List of users who are authorized to view the queue.

By default, all users are allowed to view the queue. Access is
always granted if the invoking user is the super-user or the
$mail_owner user. Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list. The username
“unknown” is used for processes whose real UID is not found in the
password file.

Specify a list of user names, “/file/name” or “type:table” patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A “/file/name”
pattern is replaced
by its contents; a “type:table” lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify “!pattern”
to exclude a user name from the list. The form “!/file/name” is
supported only in Postfix version 2.4 and later.

This feature is available in Postfix 2.2 and later.

List of users who are authorized to submit mail with the sendmail(1)
command (and with the privileged postdrop(1) helper command).

By default, all users are allowed to submit mail. Otherwise, the
real UID of the process is looked up in the system password file,
and access is granted only if the corresponding login name is on
the access list. The username “unknown” is used for processes
whose real UID is not found in the password file. To deny mail
submission access to all users specify an empty list.

Specify a list of user names, “/file/name” or “type:table” patterns,
separated by commas and/or whitespace. The list is matched left to right,
and the search stops on the first match. A “/file/name” pattern is
replaced by its contents;
a “type:table” lookup table is matched when a name matches a lookup key
(the lookup result is ignored). Continue long lines by starting the
next line with whitespace. Specify “!pattern” to exclude a user
name from the list. The form “!/file/name” is supported only in
Postfix version 2.4 and later.

Example:

authorized_submit_users = !www, static:all

This feature is available in Postfix 2.2 and later.

What remote SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address.

By default, only trusted clients are allowed to specify XVERP.

This parameter was introduced with Postfix version 1.1. Postfix
version 2.1 renamed this parameter to smtpd_authorized_verp_clients
and changed the default to none.

Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it), “/file/name” or “type:table” patterns. A “/file/name”
pattern is replaced by its contents; a “type:table” lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored). Continue long lines by starting the next line
with whitespace. Specify “!pattern” to exclude an address or network
block from the list. The form “!/file/name” is supported only in
Postfix version 2.4 and later.

Note: IP version 6 address information must be specified inside
[] in the authorized_verp_clients value, and in files
specified with “/file/name”. IP version 6 addresses contain the
“:” character, and would otherwise be confused with a “type:table”
pattern.

Produce additional bounce(8) logfile records that can be read by
Postfix versions before 2.0. The current and more extensible “name =
value” format is needed in order to implement more sophisticated
functionality.

This feature is available in Postfix 2.1 and later.

The per-table I/O buffer size for programs that create Berkeley DB
hash or btree tables. Specify a byte count.

This feature is available in Postfix 2.0 and later.

The per-table I/O buffer size for programs that read Berkeley DB
hash or btree tables. Specify a byte count.

This feature is available in Postfix 2.0 and later.

Where the Postfix SMTP client should deliver mail when it detects
a “mail loops back to myself” error condition. This happens when
the local MTA is the best SMTP mail exchanger for a destination
not listed in $mydestination, $inet_interfaces, $proxy_interfaces,
$virtual_alias_domains, or $virtual_mailbox_domains. By default,
the Postfix SMTP client returns such mail as undeliverable.

Specify, for example, “best_mx_transport = local” to pass the mail
from the Postfix SMTP client to the local(8) delivery agent. You
can specify
any message delivery “transport” or “transport:nexthop” that is
defined in the master.cf file. See the transport(5) manual page
for the syntax and meaning of “transport” or “transport:nexthop”.

However, this feature is expensive because it ties up a Postfix
SMTP client process while the local(8) delivery agent is doing its
work. It is more efficient (for Postfix) to list all hosted domains
in a table or database.

Whether or not to use the local biff service. This service sends
“new mail” notifications to users who have requested new mail
notification with the UNIX command “biff y”.

For compatibility reasons this feature is on by default. On systems
with lots of interactive users, the biff service can be a performance
drain. Specify “biff = no” in main.cf to disable.

Optional lookup tables for content inspection as specified in
the body_checks(5) manual page.

Note: with Postfix versions before 2.0, these rules inspect
all content after the primary message headers.

How much text in a message body segment (or attachment, if you
prefer to use that term) is subjected to body_checks inspection.
The amount of text is limited to avoid scanning huge attachments.

This feature is available in Postfix 2.0 and later.

The recipient of postmaster notifications with the message headers
of mail that Postfix did not deliver and of SMTP conversation
transcripts of mail that Postfix did not receive. This feature is
enabled with the notify_classes parameter.

Consider a bounce message as undeliverable, when delivery fails
with a temporary error, and the time in the queue has reached the
bounce_queue_lifetime limit. By default, this limit is the same
as for regular mail.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

Specify 0 when mail delivery should be tried only once.

This feature is available in Postfix 2.1 and later.

The name of the bounce(8) service. This service maintains a record
of failed delivery attempts and generates non-delivery notifications.

This feature is available in Postfix 2.0 and later.

The maximal amount of original message text that is sent in a
non-delivery notification. Specify a byte count. A message is
returned as either message/rfc822 (the complete original) or as
text/rfc822-headers (the headers only). With Postfix version 2.4
and earlier, a message is always returned as message/rfc822 and is
truncated when it exceeds the size limit.

Notes:

Pathname of a configuration file with bounce message templates.
These override the built-in templates of delivery status notification
(DSN) messages for undeliverable mail, delayed mail, successful
delivery, or delivery verification. The bounce(5) manual page
describes how to edit and test template files.

Template message body text may contain $name references to
Postfix configuration parameters. The result of $name expansion can
be previewed with “postconf -b file_name” before the file
is placed into the Postfix configuration directory.

This feature is available in Postfix 2.3 and later.

Enable interoperability with remote SMTP clients that implement an obsolete
version of the AUTH command (RFC 4954). Examples of such clients
are MicroSoft Outlook Express version 4 and MicroSoft Exchange
version 5.0.

Specify “broken_sasl_auth_clients = yes” to have Postfix advertise
AUTH support in a non-standard way.

What addresses are subject to canonical_maps address mapping.
By default, canonical_maps address mapping is applied to envelope
sender and recipient addresses, and to header sender and header
recipient addresses.

Specify one or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient

This feature is available in Postfix 2.2 and later.

Optional address mapping lookup tables for message headers and
envelopes. The mapping is applied to both sender and recipient
addresses, in both envelopes and in headers, as controlled
with the canonical_classes parameter. This is typically used
to clean up dirty addresses from legacy mail systems, or to replace
login names by Firstname.Lastname. The table format and lookups
are documented in canonical(5). For an overview of Postfix address
manipulations see the ADDRESS_REWRITING_README document.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.
Note: these lookups are recursive.

If you use this feature, run “postmap /etc/postfix/canonical” to
build the necessary DBM or DB file after every change. The changes
will become visible after a minute or so. Use “postfix reload”
to eliminate the delay.

Note: with Postfix version 2.2, message header address mapping
happens only when message header address rewriting is enabled:

To get the behavior before Postfix version 2.2, specify
“local_header_rewrite_clients = static:all”.

Examples:

canonical_maps = dbm:/etc/postfix/canonical
canonical_maps = hash:/etc/postfix/canonical

The name of the cleanup(8) service. This service rewrites addresses
into the standard form, and performs canonical(5) address mapping
and virtual(5) aliasing.

This feature is available in Postfix 2.0 and later.

The location of all postfix administrative commands.

The local(8) delivery agent working directory for delivery to
external commands. Failure to change directory causes the delivery
to be deferred.

The command_execution_directory value is not subject to Postfix
configuration parameter $name expansion. Instead, the following
$name expansions are done on command_execution_directory before the
directory is used. Expansion happens in the context
of the delivery request. The result of $name expansion is filtered
with the character set that is specified with the
execution_directory_expansion_filter parameter.

$user

The recipient’s username.

$shell

The recipient’s login shell pathname.

$home

The recipient’s home directory.

$recipient

The full recipient address.

$extension

The optional recipient address extension.

$domain

The recipient domain.

$local

The entire recipient localpart.

$recipient_delimiter

The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier).

${name?value}

${name?{value}} (Postfix ≥ 3.0)

Expands to value when $name is non-empty.

${name:value}

${name:{value}} (Postfix ≥ 3.0)

Expands to value when $name is empty.

${name?{value1}:{value2}} (Postfix ≥ 3.0)

Expands to value1 when $name is non-empty,
value2 otherwise.

Instead of $name you can also specify ${name} or $(name).

This feature is available in Postfix 2.2 and later.

Restrict the characters that the local(8) delivery agent allows in
$name expansions of $mailbox_command and $command_execution_directory.
Characters outside the
allowed set are replaced by underscores.

Time limit for delivery to external commands. This limit is used
by the local(8) delivery agent, and is the default time limit for
delivery by the pipe(8) delivery agent.

Note: if you set this time limit to a large value you must update the
global ipc_timeout parameter as well.

A safety net that causes Postfix to run with backwards-compatible
default settings after an upgrade to a newer Postfix version.

With backwards compatibility turned on (the main.cfcompatibility_level
value is less than the Postfix built-in value), Postfix looks for
settings that are left at their implicit default value, and logs a
message when a backwards-compatible default setting is required.

using backwards-compatible default setting name=value
    to [accept a specific client request]

using backwards-compatible default setting name=value
    to [enable specific Postfix behavior]

See COMPATIBILITY_README for specific message details. If such
a message is logged in the context of a legitimate request, the
system administrator should make the backwards-compatible setting
permanent in main.cf or master.cf, for example:

# postconfname=value
# postfix reload

When no more backwards-compatible settings need to be made
permanent, the administrator should turn off backwards compatibility
by updating the compatibility_level setting in main.cf:

# postconf compatibility_level=N
# postfix reload

For N specify the number that is logged in your postfix(1)
warning message:

warning: To disable backwards compatibility use "postconf
    compatibility_level=N" and "postfix reload"

Starting with Postfix version 3.6, the compatibility level in
the above warning message is the Postfix version that introduced
the last incompatible change. The level is formatted as
major.minor.patch, where patch is usually omitted and
defaults to zero. Earlier compatibility levels are 0, 1 and 2.

NOTE: this also introduces support for the “<level”,
“<=level”, and other operators to compare compatibility levels.
With the standard operators “<“, “<=”, etc., compatibility
level “3.10” would be smaller than “3.9” which is undesirable.

This feature is available in Postfix 3.0 and later.

The default location of the Postfix main.cf and master.cf
configuration files. This can be overruled via the following
mechanisms:

• The MAIL_CONFIG environment variable (daemon processes
  and commands).

• The “-c” command-line option (commands only).

With Postfix commands that run with set-gid privileges, a
config_directory override either requires root privileges, or it
requires that the directory is listed with the alternate_config_directories
parameter in the default main.cf file.

After sending a “your message is delayed” notification, inform
the sender when the delay clears up. This can result in a sudden
burst of notifications at the end of a prolonged network outage,
and is therefore disabled by default.

See also: delay_warning_time.

This feature is available in Postfix 3.0 and later.

Time limit for connection cache connect, send or receive
operations. The time limit is enforced in the client.

This feature is available in Postfix 2.3 and later.

The name of the scache(8) connection cache service. This service
maintains a limited pool of cached sessions.

This feature is available in Postfix 2.2 and later.

How frequently the scache(8) server logs usage statistics with
connection cache hit and miss rates for logical destinations and for
physical endpoints.

The maximal time-to-live value that the scache(8) connection
cache server
allows. Requests that specify a larger TTL will be stored with the
maximum allowed TTL. The purpose of this additional control is to
protect the infrastructure against careless people. The cache TTL
is already bounded by $max_idle.

After the message is queued, send the entire message to the
specified transport:destination. The transport name
specifies the first field of a mail delivery agent definition in
master.cf; the syntax of the next-hop destination is described
in the manual page of the corresponding delivery agent. More
information about external content filters is in the Postfix
FILTER_README file.

Notes:

Search path for Cyrus SASL application configuration files,
currently used only to locate the $smtpd_sasl_path.conf file.
Specify zero or more directories separated by a colon character,
or an empty value to use Cyrus SASL’s built-in search path.

This feature is available in Postfix 2.5 and later when compiled
with Cyrus SASL 2.1.22 or later.

The directory with Postfix support programs and daemon programs.
These should not be invoked directly by humans. The directory must
be owned by root.

How a Postfix daemon process handles errors while opening lookup
tables: gradual degradation or immediate termination.

no (default)

Gradual degradation: a
daemon process logs a message of type “error” and continues execution
with reduced functionality. Features that do not depend on the
unavailable table will work normally, while features that depend
on the table will result in a type “warning” message.
When
the notify_classes parameter value contains the “data” class, the
Postfix SMTP server and client will report transcripts of sessions
with an error because a table is unavailable.

yes (historical behavior)

Immediate
termination: a daemon process logs a type “fatal” message and
terminates immediately. This option reduces the number of possible
code paths through Postfix, and may therefore be slightly more
secure than the default.

For the sake of sanity, the number of type “error” messages is
limited to 13 over the lifetime of a daemon process.

This feature is available in Postfix 2.9 and later.

How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The directory with Postfix-writable data files (for example:
caches, pseudo-random numbers). This directory must be owned by
the mail_owner account, and must not be shared with non-Postfix
software.

This feature is available in Postfix 2.5 and later.

The increment in verbose logging level when a nexthop destination,
remote client or server name or network address matches a pattern
given with the debug_peer_list parameter.

Per-nexthop debug logging is available in Postfix 3.6 and later.

Optional list of nexthop destination, remote client or server
name or network address patterns that, if matched, cause the verbose
logging level to increase by the amount specified in $debug_peer_level.

Per-nexthop debug logging is available in Postfix 3.6 and later.

Specify domain names, network/netmask patterns, “/file/name”
patterns or “type:table” lookup tables. The right-hand side result
from “type:table” lookups is ignored.

Pattern matching of domain names is controlled by the presence
or absence of “debug_peer_list” in the parent_domain_matches_subdomains
parameter value.

Examples:

debug_peer_list = 127.0.0.1
debug_peer_list = example.com

The external command to execute when a Postfix daemon program is
invoked with the -D option.

Use “command .. & sleep 5” so that the debugger can attach before
the process marches on. If you use an X-based debugger, be sure to
set up your XAUTHORITY environment variable before starting Postfix.

Note: the command is subject to $name expansion, before it is
passed to the default command interpreter. Specify “$$” to
produce a single “$” character.

Example:

debugger_command =
    PATH=/usr/bin:/usr/X11R6/bin
    ddd $daemon_directory/$process_name $process_id & sleep 5

The default database type for use in newaliases(1), postalias(1)
and postmap(1) commands. On many UNIX systems the default type is
either dbm or hash. The default setting is frozen
when the Postfix system is built.

Examples:

default_database_type = hash
default_database_type = dbm

How often the Postfix queue manager’s scheduler is allowed to
preempt delivery of one message with another.

Each transport maintains a so-called “available delivery slot counter”
for each message. One message can be preempted by another one when
the other message can be delivered using no more delivery slots
(i.e., invocations of delivery agents) than the current message
counter has accumulated (or will eventually accumulate – see about
slot loans below). This parameter controls how often the counter is
incremented – it happens after each default_delivery_slot_cost
recipients have been delivered.

The cost of 0 is used to disable the preempting scheduling completely.
The minimum value the scheduling algorithm can use is 2 – use it
if you want to maximize the message throughput rate. Although there
is no maximum, it doesn’t make much sense to use values above say
50.

The only reason why the value of 2 is not the default is the way
this parameter affects the delivery of mailing-list mail. In the
worst case, delivery can take somewhere between (cost 1/cost)
and (cost/cost-1) times more than if the preemptive scheduler was
disabled. The default value of 5 turns out to provide reasonable
message response times while making sure the mailing-list deliveries
are not extended by more than 20-25 percent even in the worst case.

Use transport_delivery_slot_cost to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

Examples:

default_delivery_slot_cost = 0
default_delivery_slot_cost = 2

The default value for transport-specific _delivery_slot_discount
settings.

This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.

Use transport_delivery_slot_discount to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

The default value for transport-specific _delivery_slot_loan
settings.

This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
transport_delivery_slot_discount percent of the required amount
plus transport_delivery_slot_loan still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.

Use transport_delivery_slot_loan to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

Optional filter to replace the delivery status code or explanatory
text of successful or unsuccessful deliveries. This does not allow
the replacement of a successful status code (2.X.X) with an
unsuccessful status code (4.X.X or 5.X.X) or vice versa.

Note: the (smtp|lmtp)_delivery_status_filter is applied only
once per recipient: when delivery is successful, when delivery is
rejected with 5XX, or when there are no more alternate MX or A
destinations. Use smtp_reply_filter or lmtp_reply_filter to inspect
responses for all delivery attempts.

The following parameters can be used to implement a filter for
specific delivery agents: lmtp_delivery_status_filter,
local_delivery_status_filter, pipe_delivery_status_filter,
smtp_delivery_status_filter or virtual_delivery_status_filter. These
parameters support the same filter syntax as described here.

Specify zero or more “type:table” lookup table names, separated
by comma or whitespace. For each successful or unsuccessful delivery
to a recipient, the tables are queried in the specified order with
one line of text that is structured as follows:

enhanced-status-code SPACE explanatory-text

The first table match wins. The lookup result must have the
same structure as the query, a successful status code (2.X.X) must
be replaced with a successful status code, an unsuccessful status
code (4.X.X or 5.X.X) must be replaced with an unsuccessful status
code, and the explanatory text field must be non-empty. Other results
will result in a warning.

Example 1: convert specific soft TLS errors into hard errors,
by overriding the first number in the enhanced status code.

/etc/postfix/main.cf:
    smtp_delivery_status_filter = pcre:/etc/postfix/smtp_dsn_filter

/etc/postfix/smtp_dsn_filter:
    /^4(.d .d  TLS is required, but host S  refused to start TLS: . )/
        5$1
    /^4(.d .d  TLS is required, but was not offered by host . )/
        5$1
    # Do not change the following into hard bounces. They may
    # result from a local configuration problem.
    # 4.d .d  TLS is required, but our TLS engine is unavailable
    # 4.d .d  TLS is required, but unavailable
    # 4.d .d  Cannot start TLS: handshake failure

Example 2: censor the per-recipient delivery status text so
that it does not reveal the destination command or filename
when a remote sender requests confirmation of successful delivery.

/etc/postfix/main.cf:
    local_delivery_status_filter = pcre:/etc/postfix/local_dsn_filter

/etc/postfix/local_dsn_filter:
    /^(2S  delivered to file). /    $1
    /^(2S  delivered to command). / $1

Notes:

This feature is available in Postfix 3.0 and later.

How many pseudo-cohorts must suffer connection or handshake
failure before a specific destination is considered unavailable
(and further delivery is suspended). Specify zero to disable this
feature. A destination’s pseudo-cohort failure count is reset each
time a delivery completes without connection or handshake failure
for that specific destination.

A pseudo-cohort is the number of deliveries equal to a destination’s
delivery concurrency.

Use transport_destination_concurrency_failed_cohort_limit to specify
a transport-specific override, where transport is the master.cf
name of the message delivery transport.

This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions.

The default maximal number of parallel deliveries to the same
destination. This is the default limit for delivery via the lmtp(8),
pipe(8), smtp(8) and virtual(8) delivery agents.
With a per-destination recipient limit > 1, a destination is a domain,
otherwise it is a recipient.

Use transport_destination_concurrency_limit to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

The per-destination amount of delivery concurrency negative
feedback, after a delivery completes with a connection or handshake
failure. Feedback values are in the range 0..1 inclusive. With
negative feedback, concurrency is decremented at the beginning of
a sequence of length 1/feedback. This is unlike positive feedback,
where concurrency is incremented at the end of a sequence of length
1/feedback.

As of Postfix version 2.5, negative feedback cannot reduce
delivery concurrency to zero. Instead, a destination is marked
dead (further delivery suspended) after the failed pseudo-cohort
count reaches $default_destination_concurrency_failed_cohort_limit
(or $transport_destination_concurrency_failed_cohort_limit).
To make the scheduler completely immune to connection or handshake
failures, specify a zero feedback value and a zero failed pseudo-cohort
limit.

Specify one of the following forms:

number

number / number

Constant feedback. The value must be in the range 0..1 inclusive.
The default setting of “1” is compatible with Postfix versions
before 2.5, where a destination’s delivery concurrency is throttled
down to zero (and further delivery suspended) after a single failed
pseudo-cohort.

number / concurrency

Variable feedback of “number / (delivery concurrency)”.
The number must be in the range 0..1 inclusive. With
number equal to “1”, a destination’s delivery concurrency
is decremented by 1 after each failed pseudo-cohort.

A pseudo-cohort is the number of deliveries equal to a destination’s
delivery concurrency.

Use transport_destination_concurrency_negative_feedback
to specify a transport-specific override, where transport
is the master.cf
name of the message delivery transport.

This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions.

The per-destination amount of delivery concurrency positive
feedback, after a delivery completes without connection or handshake
failure. Feedback values are in the range 0..1 inclusive. The
concurrency increases until it reaches the per-destination maximal
concurrency limit. With positive feedback, concurrency is incremented
at the end of a sequence with length 1/feedback. This is unlike
negative feedback, where concurrency is decremented at the start
of a sequence of length 1/feedback.

Specify one of the following forms:

number

number / number

Constant feedback. The value must be in the range 0..1
inclusive. The default setting of “1” is compatible with Postfix
versions before 2.5, where a destination’s delivery concurrency
doubles after each successful pseudo-cohort.

number / concurrency

Variable feedback of “number / (delivery concurrency)”.
The number must be in the range 0..1 inclusive. With
number equal to “1”, a destination’s delivery concurrency
is incremented by 1 after each successful pseudo-cohort.

A pseudo-cohort is the number of deliveries equal to a destination’s
delivery concurrency.

Use transport_destination_concurrency_positive_feedback
to specify a transport-specific override, where transport
is the master.cf name of the message delivery transport.

This feature is available in Postfix 2.5 and later.

The default amount of delay that is inserted between individual
message deliveries to the same destination and over the same message
delivery transport. Specify a non-zero value to rate-limit those
message deliveries to at most one per $default_destination_rate_delay.

The resulting behavior depends on the value of the corresponding
per-destination recipient limit.

To enable the delay, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit).

Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds).

NOTE: the delay is enforced by the queue manager. The delay
timer state does not survive “postfix reload” or “postfix
stop“.

Use transport_destination_rate_delay to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

NOTE: with a non-zero _destination_rate_delay, specify a
transport_destination_concurrency_failed_cohort_limit of 10
or more to prevent Postfix from deferring all mail for the same
destination after only one connection or handshake error.

This feature is available in Postfix 2.5 and later.

The default maximal number of recipients per message delivery.
This is the default limit for delivery via the lmtp(8), pipe(8),
smtp(8) and virtual(8) delivery agents.

Setting this parameter to a value of 1 affects email deliveries
as follows:

Use transport_destination_recipient_limit to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

The default value for the extra per-transport limit imposed on the
number of in-memory recipients. This extra recipient space is
reserved for the cases when the Postfix queue manager’s scheduler
preempts one message with another and suddenly needs some extra
recipient slots for the chosen message in order to avoid performance
degradation.

Use transport_extra_recipient_limit to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

When a content_filter or FILTER request specifies no explicit
next-hop destination, use $default_filter_nexthop instead; when
that value is empty, use the domain in the recipient address.
Specify “default_filter_nexthop = $myhostname” for compatibility
with Postfix version 2.6 and earlier, or specify an explicit next-hop
destination with each content_filter value or FILTER action.

This feature is available in Postfix 2.7 and later.

How many recipients a message must have in order to invoke the
Postfix queue manager’s scheduling algorithm at all. Messages
which would never accumulate at least this many delivery slots
(subject to slot cost parameter as well) are never preempted.

Use transport_minimum_delivery_slots to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

The default rights used by the local(8) delivery agent for delivery
to an external file or command. These rights are used when delivery
is requested from an aliases(5) file that is owned by root, or
when delivery is done on behalf of root. DO NOT SPECIFY A
PRIVILEGED USER OR THE POSTFIX OWNER.

The default maximal number of Postfix child processes that provide
a given service. This limit can be overruled for specific services
in the master.cf file.

The default Postfix SMTP server response template for a request that is
rejected by an RBL-based restriction. This template can be overruled
by specific entries in the optional rbl_reply_maps lookup table.

This feature is available in Postfix 2.0 and later.

The template does not support Postfix configuration parameter $name
substitution. Instead, it supports exactly one level of $name
substitution for the following attributes:

$client

The client hostname and IP address, formatted as name[address].

$client_address

The client IP address.

$client_name

The client hostname or “unknown”. See reject_unknown_client_hostname
for more details.

$reverse_client_name

The client hostname from address->name lookup, or “unknown”.
See reject_unknown_reverse_client_hostname for more details.

$helo_name

The hostname given in HELO or EHLO command or empty string.

$rbl_class

The denylisted entity type: Client host, Helo command, Sender
address, or Recipient address.

$rbl_code

The numerical SMTP response code, as specified with the
maps_rbl_reject_code configuration parameter. Note: The numerical
SMTP response code is required, and must appear at the start of the
reply. With Postfix version 2.3 and later this information may be followed
by an RFC 3463 enhanced status code.

$rbl_domain

The RBL domain where $rbl_what is denylisted.

$rbl_reason

The reason why $rbl_what is denylisted, or an empty string.

$rbl_what

The entity that is denylisted (an IP address, a hostname, a domain
name, or an email address whose domain was denylisted).

$recipient

The recipient address or <> in case of the null address.

$recipient_domain

The recipient domain or empty string.

$recipient_name

The recipient address localpart or <> in case of null address.

$sender

The sender address or <> in case of the null address.

$sender_domain

The sender domain or empty string.

$sender_name

The sender address localpart or <> in case of the null address.

${name?value}

${name?{value}} (Postfix ≥ 3.0)

Expands to value when $name is non-empty.

${name:value}

${name:{value}} (Postfix ≥ 3.0)

Expands to value when $name is empty.

${name?{value1}:{value2}} (Postfix ≥ 3.0)

Expands to value1 when $name is non-empty,
value2 otherwise.

Instead of $name you can also specify ${name} or $(name).

Note: when an enhanced status code is specified in an RBL reply
template, it is subject to modification. The following transformations
are needed when the same RBL reply template is used for client,
helo, sender, or recipient access restrictions.

• When rejecting a sender address, the Postfix SMTP server
  will transform a recipient DSN status (e.g., 4.1.1-4.1.6) into the
  corresponding sender DSN status, and vice versa.

• When rejecting non-address information (such as the HELO
  command argument or the client hostname/address), the Postfix SMTP
  server will transform a sender or recipient DSN status into a generic
  non-address DSN status (e.g., 4.0.0).

The default per-transport upper limit on the number of in-memory
recipients. These limits take priority over the global
qmgr_message_recipient_limit after the message has been assigned
to the respective transports. See also default_extra_recipient_limit
and qmgr_message_recipient_minimum.

Use transport_recipient_limit to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

The default per-transport maximum delay between refilling recipients.
When not all message recipients fit into memory at once, keep loading
more of them at least once every this many seconds. This is used to
make sure the recipients are refilled in a timely manner even when
$default_recipient_refill_limit is too high for too slow deliveries.

Use transport_recipient_refill_delay to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

This feature is available in Postfix 2.4 and later.

The default per-transport limit on the number of recipients refilled at
once. When not all message recipients fit into memory at once, keep
loading more of them in batches of at least this many at a time. See also
$default_recipient_refill_delay, which may result in recipient batches
lower than this when this limit is too high for too slow deliveries.

Use transport_recipient_refill_limit to specify a
transport-specific override, where transport is the master.cf
name of the message delivery transport.

This feature is available in Postfix 2.4 and later.

The default mail delivery transport and next-hop destination for
destinations that do not match $mydestination, $inet_interfaces,
$proxy_interfaces, $virtual_alias_domains, $virtual_mailbox_domains,
or $relay_domains. This information can be overruled with the
sender_dependent_default_transport_maps parameter and with the
transport(5) table.

In order of decreasing precedence, the nexthop destination is taken
from $sender_dependent_default_transport_maps, $default_transport,
$sender_dependent_relayhost_maps, $relayhost, or from the recipient
domain.

Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in master.cf.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent. In the case of
SMTP or LMTP, specify one or more destinations separated by comma or
whitespace (with Postfix 3.5 and later).

Example:

default_transport = uucp:relayhostname

The default amount of delay that is inserted between individual
message deliveries over the same message delivery transport,
regardless of destination. Specify a non-zero value to rate-limit
those message deliveries to at most one per $default_transport_rate_delay.

Use transport_transport_rate_delay to specify a
transport-specific override, where the initial transport is
the master.cf name of the message delivery transport.

Example: throttle outbound SMTP mail to at most 3 deliveries
per minute.

/etc/postfix/main.cf:
    smtp_transport_rate_delay = 20s

To enable the delay, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit).

Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds).

NOTE: the delay is enforced by the queue manager.

This feature is available in Postfix 3.1 and later.

The two default VERP delimiter characters. These are used when
no explicit delimiters are specified with the SMTP XVERP command
or with the “sendmail -XV” command-line option (Postfix 2.2
and earlier: -V). Specify characters that are allowed by the
verp_delimiter_filter setting.

This feature is available in Postfix 1.1 and later.

The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the “defer” restriction.

Do not change this unless you have a complete understanding of RFC 5321.

The name of the defer service. This service is implemented by the
bounce(8) daemon and maintains a record
of failed delivery attempts and generates non-delivery notifications.

This feature is available in Postfix 2.0 and later.

The names of message delivery transports that should not deliver mail
unless someone issues “sendmail -q” or equivalent. Specify zero
or more mail delivery transport names that appear in the
first field of master.cf.

Example:

defer_transports = smtp

The maximal number of digits after the decimal point when logging
sub-second delay values. Specify a number in the range 0..6.

Large delay values are rounded off to an integral number of seconds;
delay values below the delay_logging_resolution_limit are logged
as “0”, and delay values under 100s are logged with at most two-digit
precision.

The format of the “delays=a/b/c/d” logging is as follows:

This feature is available in Postfix 2.3 and later.

The recipient of postmaster notifications with the message headers
of mail that cannot be delivered within $delay_warning_time time
units.

See also: delay_warning_time, notify_classes.

The time after which the sender receives a copy of the message
headers of mail that is still queued. The confirm_delay_cleared
parameter controls sender notification when the delay clears up.

To enable this feature, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit).

Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

See also: delay_notice_recipient, notify_classes, confirm_delay_cleared.

The maximal number of attempts to acquire an exclusive lock on a
mailbox file or bounce(8) logfile.

The time between attempts to acquire an exclusive lock on a mailbox
file or bounce(8) logfile.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

Make the queue manager’s feedback algorithm verbose for performance
analysis purposes.

This feature is available in Postfix 2.5 and later.

Automatically detect 8BITMIME body content by looking at
Content-Transfer-Encoding: message headers; historically, this
behavior was hard-coded to be “always on”.

This feature is available in Postfix 2.5 and later.

Disable DNS lookups in the Postfix SMTP and LMTP clients. When
disabled, hosts are looked up with the getaddrinfo() system
library routine which normally also looks in /etc/hosts. As of
Postfix 2.11, this parameter is deprecated; use smtp_dns_support_level
instead.

DNS lookups are enabled by default.

Turn off MIME processing while receiving mail. This means that no
special treatment is given to Content-Type: message headers, and
that all text after the initial message headers is considered to
be part of the message body.

This feature is available in Postfix 2.0 and later.

Mime input processing is enabled by default, and is needed in order
to recognize MIME headers in message content.

Disable the conversion of 8BITMIME format to 7BIT format. Mime
output conversion is needed when the destination does not advertise
8BITMIME support.

This feature is available in Postfix 2.0 and later.

Disable sending one bounce report per recipient.

The default, one per recipient, is what ezmlm needs.

This feature is available in Postfix 1.1 and later.

Disable the SMTP VRFY command. This stops some techniques used to
harvest email addresses.

Example:

disable_vrfy_command = no

Enable a workaround for future libc incompatibility. The Postfix
implementation of RFC 2308 negative reply caching relies on the
promise that res_query() and res_search() invoke res_send(), which
returns the server response in an application buffer even if the
requested record does not exist. If this promise is broken, specify
“yes” to enable a workaround for DNS reputation lookups.

This feature is available in Postfix 3.1 and later.

A debugging aid to artificially delay DNS responses.

This feature is available in Postfix 2.8.

The name of the dnsblog(8) service entry in master.cf. This
service performs DNS allow/denylist lookups.

This feature is available in Postfix 2.8 and later.

The DNS query type (default: “ns”) and DNS query name (default:
“.”) that Postfix may use to determine whether DNSSEC validation
is available.

Background: DNSSEC validation is needed for Postfix DANE support;
this ensures that Postfix receives TLSA records with secure TLS
server certificate info. When DNSSEC validation is unavailable,
mail deliveries using opportunistic DANE will not be protected
by server certificate info in TLSA records, and mail deliveries
using mandatory DANE will not be made at all.

By default, a Postfix process will send a DNSSEC probe after
1) the process made a DNS query that requested DNSSEC validation,
2) the process did not receive a DNSSEC validated response to this
query or to an earlier query, and 3) the process did not already
send a DNSSEC probe.

When the DNSSEC probe has no response, or when the response is
not DNSSEC validated, Postfix logs a warning that DNSSEC validation
may be unavailable.

Example:

warning: DNSSEC validation may be unavailable
warning: reason: dnssec_probe 'ns:.' received a response that is not DNSSEC validated
warning: reason: dnssec_probe 'ns:.' received no response: Server failure

Possible reasons why DNSSEC validation may be unavailable:

By default, the DNSSEC probe asks for the DNS root zone NS
records, because resolvers should always have that information
cached. If Postfix runs on a network where the DNS root zone is not
reachable, specify a different probe, or specify an empty dnssec_probe
value to disable the feature.

This feature is available in Postfix 3.6 and later. It was backported
to Postfix versions 3.5.9, 3.4.19, 3.3.16. 3.2.21.

Don’t remove queue files and save them to the “saved” mail queue.
This is a debugging aid. To inspect the envelope information and
content of a Postfix queue file, use the postcat(1) command.

The sender address of postmaster notifications that are generated
by the mail system. All mail to this address is silently discarded,
in order to terminate mail bounce loops.

The maximal number of addresses remembered by the address
duplicate filter for aliases(5) or virtual(5) alias expansion, or
for showq(8) queue displays.

The sender_dependent_default_transport_maps search string that
will be used instead of the null sender address.

This feature is available in Postfix 2.7 and later.

The lookup key to be used in local_login_sender_maps tables, instead
of the null sender address.

This feature is available in Postfix 3.6 and later.

The recipient of mail addressed to the null address. Postfix does
not accept such addresses in SMTP commands, but they may still be
created locally as the result of configuration or software error.

The sender_dependent_relayhost_maps search string that will be
used instead of the null sender address.

This feature is available in Postfix 2.5 and later. With
earlier versions, sender_dependent_relayhost_maps lookups were
skipped for the null sender address.

Report mail delivery errors to the address specified with the
non-standard Errors-To: message header, instead of the envelope
sender address (this feature is removed with Postfix version 2.2, is
turned off by default with Postfix version 2.1, and is always turned on
with older Postfix versions).

Enable ‘transitional’ compatibility between IDNA2003 and IDNA2008,
when converting UTF-8 domain names to/from the ASCII form that is
used for DNS lookups. Specify “yes” for compatibility with Postfix
≤ 3.1 (not recommended). This affects the conversion of domain
names that contain for example the German sz and the Greek zeta.
See http://unicode.org/cldr/utility/idna.jsp for more examples.

This feature is available in Postfix 3.2 and later.

Enable long, non-repeating, queue IDs (queue file names). The
benefit of non-repeating names is simpler logfile analysis and
easier queue migration (there is no need to run “postsuper” to
change queue file names that don’t match their message file inode
number).

Note: see below for how to convert long queue file names to
Postfix ≤ 2.8.

Changing the parameter value to “yes” has the following effects:

Changing the parameter value to “no” has the following effects:

Before migration to Postfix ≤ 2.8, the following commands
are required to convert long queue file names into short names:

# postfix stop
# postconf enable_long_queue_ids=no
# postsuper

Repeat the postsuper command until it reports no more queue file
name changes.

This feature is available in Postfix 2.9 and later.

Enable support for the original recipient address after an
address is rewritten to a different address (for example with
aliasing or with canonical mapping).

The original recipient address is used as follows:

Final delivery

With “enable_original_recipient =
yes”, the original recipient address is stored in the X-Original-To
message header. This header may be used to distinguish between
different recipients that share the same mailbox.

Recipient deduplication

With “enable_original_recipient
= yes”, the cleanup(8) daemon performs duplicate recipient elimination
based on the content of (original recipient, maybe-rewritten
recipient) pairs. Otherwise, the cleanup(8) daemon performs duplicate
recipient elimination based only on the maybe-rewritten recipient
address.

Note: with Postfix ≤ 3.2 the “setting enable_original_recipient
= no” breaks address verification for addresses that are
aliased or otherwise rewritten (Postfix is unable to store the
address verification result under the original probe destination
address; instead, it can store the result only under the rewritten
address).

This feature is available in Postfix 2.1 and later. Postfix
version 2.0 behaves as if this parameter is always set to yes.
Postfix versions before 2.0 have no support for the original recipient
address.

Enable non-delivery, success, and delay notifications that link
to the original message by including a References: and In-Reply-To:
header with the original Message-ID value. There are advantages and
disadvantages to consider.

advantage

This allows mail readers to present
a delivery status notification in the same email thread as the original
message.

disadvantage

This makes it easy for users to
mistakenly delete the whole email thread (all related messages),
instead of deleting only the non-delivery notification.

This feature is available in Postfix 3.6 and later.

The recipient of postmaster notifications about mail delivery
problems that are caused by policy, resource, software or protocol
errors. These notifications are enabled with the notify_classes
parameter.

The name of the error(8) pseudo delivery agent. This service always
returns mail as undeliverable.

This feature is available in Postfix 2.0 and later.

Restrict the characters that the local(8) delivery agent allows
in $name expansions of $command_execution_directory. Characters
outside the allowed set are replaced by underscores.

This feature is available in Postfix 2.2 and later.

When delivering to an alias “aliasname” that has an
“owner-aliasname” companion alias, set the envelope sender
address to the expansion of the “owner-aliasname” alias.
Normally, Postfix sets the envelope sender address to the name of
the “owner-aliasname” alias.

The list of environment variables that a Postfix process will export
to non-Postfix processes. The TZ variable is needed for sane
time keeping on System-V-ish systems.

Specify a list of names and/or name=value pairs, separated by
whitespace or comma. Specify “{ name=value }” to protect whitespace
or comma in parameter values (whitespace after the opening “{” and
before the closing “}”
is ignored). The form name=value is supported with Postfix version
2.1 and later; the use of {} is supported with Postfix 3.0 and
later.

Example:

export_environment = TZ PATH=/bin:/usr/bin

The maximal number of recipient addresses that Postfix will extract
from message headers when mail is submitted with “sendmail -t“.

This feature was removed in Postfix version 2.1.

Optional list of relay hosts for SMTP destinations that can’t be
found or that are unreachable. With Postfix 2.3 this parameter
is renamed to smtp_fallback_relay.

By default, mail is returned to the sender when a destination is
not found, and delivery is deferred when a destination is unreachable.

The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups. If you specify multiple SMTP
destinations, Postfix will try them in the specified order.

Note: before Postfix 2.2, do not use the fallback_relay feature
when relaying mail
for a backup or primary MX domain. Mail would loop between the
Postfix MX host and the fallback_relay host when the final destination
is unavailable.

Postfix version 2.2 and later will not use the fallback_relay feature
for destinations that it is MX host for.

Optional message delivery transport that the local(8) delivery
agent should use for names that are not found in the aliases(5)
or UNIX password database.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Optional lookup tables with per-recipient message delivery
transports for recipients that the local(8) delivery agent could
not find in the aliases(5) or UNIX password database.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

For safety reasons, this feature does not allow $number
substitutions in regular expression maps.

This feature is available in Postfix 2.3 and later.

Optional list of destinations that are eligible for per-destination
logfiles with mail that is queued to those destinations.

By default, Postfix maintains “fast flush” logfiles only for
destinations that the Postfix SMTP server is willing to relay to
(i.e. the default is: “fast_flush_domains = $relay_domains“; see
the relay_domains parameter in the postconf(5) manual).

Specify a list of hosts or domains, “/file/name” patterns or
“type:table” lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
“/file/name” pattern is replaced by its contents; a “type:table”
lookup table is matched when the domain or its parent domain appears
as lookup key.

Pattern matching of domain names is controlled by the presence
or absence of “fast_flush_domains” in the parent_domain_matches_subdomains
parameter value.

Specify “fast_flush_domains =” (i.e., empty) to disable the feature
altogether.

The time after which an empty per-destination “fast flush” logfile
is deleted.

You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time unit is days.

The time after which a non-empty but unread per-destination “fast
flush” logfile needs to be refreshed. The contents of a logfile
are refreshed by requesting delivery of all messages listed in the
logfile.

You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time unit is hours.

Force specific internal tests to fail, to test the handling of
errors that are difficult to reproduce otherwise.

The name of the flush(8) service. This service maintains per-destination
logfiles with the queue file names of mail that is queued for those
destinations.

This feature is available in Postfix 2.0 and later.

The maximal number of attempts to fork() a child process.

The delay between attempts to fork() a child process.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

Restrict the characters that the local(8) delivery agent allows in
$name expansions of $forward_path. Characters outside the
allowed set are replaced by underscores.

The local(8) delivery agent search list for finding a .forward
file with user-specified delivery methods. The first file that is
found is used.

The forward_path value is not subject to Postfix configuration
parameter $name expansion. Instead, the following $name expansions
are done on forward_path before the search actually happens.
The result of $name expansion is
filtered with the character set that is specified with the
forward_expansion_filter parameter.

$user

The recipient’s username.

$shell

The recipient’s login shell pathname.

$home

The recipient’s home directory.

$recipient

The full recipient address.

$extension

The optional recipient address extension.

$domain

The recipient domain.

$local

The entire recipient localpart.

$recipient_delimiter

The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier).

${name?value}

${name?{value}} (Postfix ≥ 3.0)

Expands to value when $name is non-empty.

${name:value}

${name:{value}} (Postfix ≥ 3.0)

Expands to value when $name is empty.

${name?{value1}:{value2}} (Postfix ≥ 3.0)

Expands to value1 when $name is non-empty,
value2 otherwise.

Instead of $name you can also specify ${name} or $(name).

Examples:

forward_path = /var/forward/$user
forward_path =
    /var/forward/$user/.forward$recipient_delimiter$extension,
    /var/forward/$user/.forward

Update the local(8) delivery agent’s idea of the Delivered-To:
address (see prepend_delivered_header) only once, at the start of
a delivery attempt; do not update the Delivered-To: address while
expanding aliases or .forward files.

This feature is available in Postfix 2.3 and later. With older
Postfix releases, the behavior is as if this parameter is set to
“no”. The old setting can be expensive with deeply nested aliases
or .forward files. When an alias or .forward file changes the
Delivered-To: address, it ties up one queue file and one cleanup
process instance while mail is being forwarded.

The number of subdirectory levels for queue directories listed with
the hash_queue_names parameter. Queue hashing is implemented by
creating one or more levels of directories with one-character names.
Originally, these directory names were equal to the first characters
of the queue file name, with the hexadecimal representation of the
file creation time in microseconds.

With long queue file names, queue hashing produces the same
results as with short names. The file creation time in microseconds
is converted into hexadecimal form before the result is used for
queue hashing. The base 16 encoding gives finer control over the
number of subdirectories than is possible with the base 52 encoding
of long queue file names.

After changing the hash_queue_names or hash_queue_depth parameter,
execute the command “postfix reload“.

The names of queue directories that are split across multiple
subdirectory levels.

Before Postfix version 2.2, the default list of hashed queues
was significantly larger. Claims about improvements in file system
technology suggest that hashing of the incoming and active queues
is no longer needed. Fewer hashed directories speed up the time
needed to restart Postfix.

After changing the hash_queue_names or hash_queue_depth parameter,
execute the command “postfix reload“.

The maximal number of address tokens are allowed in an address
message header. Information that exceeds the limit is discarded.
The limit is enforced by the cleanup(8) server.

Optional lookup tables for content inspection of primary non-MIME
message headers, as specified in the header_checks(5) manual page.

The format of the Postfix-generated From: header. This
setting affects the appearance of ‘full name’ information when a
local program such as /bin/mail submits a message without a From:
header through the Postfix sendmail(1) command.

Specify one of the following:

standard (default)

Produce a header formatted
as “From:name <address>“.
This is the default as of Postfix 3.3.

obsolete

Produce a header formatted as “From:address(name)“. This is the behavior
prior to Postfix 3.3.

Notes:

This feature is available in Postfix 3.3 and later.

The maximal amount of memory in bytes for storing a message header.
If a header is larger, the excess is discarded. The limit is
enforced by the cleanup(8) server.

Log warnings about problematic configuration settings, and provide
helpful suggestions.

This feature is available in Postfix 2.0 and later.

Optional pathname of a mailbox file relative to a local(8) user’s
home directory.

Specify a pathname ending in “/” for qmail-style delivery.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Examples:

home_mailbox = Mailbox
home_mailbox = Maildir/

The maximal number of Received: message headers that is allowed
in the primary message headers. A message that exceeds the limit
is bounced, in order to stop a mailer loop.

The location of Postfix HTML files that describe how to build,
configure or operate a specific Postfix subsystem or feature.

Ignore DNS MX lookups that produce no response. By default,
the Postfix SMTP client defers delivery and tries again after some
delay. This behavior is required by the SMTP standard.

Specify “ignore_mx_lookup_error = yes” to force a DNS A record
lookup instead. This violates the SMTP standard and can result in
mis-delivery of mail.

The list of environment variables that a privileged Postfix
process will import from a non-Postfix parent process, or name=value
environment overrides. Unprivileged utilities will enforce the
name=value overrides, but otherwise will not change their process
environment. Examples of relevant environment variables:

TZ

May be needed for sane time keeping on most System-V-ish systems.

DISPLAY

Needed for debugging Postfix daemons with an X-windows debugger.

XAUTHORITY

Needed for debugging Postfix daemons with an X-windows debugger.

MAIL_CONFIG

Needed to make “postfix -c” work.

POSTLOG_SERVICE

Needed to make “maillog_file” work during daemon
process initialization.

POSTLOG_HOSTNAME

Needed to make “maillog_file” work during daemon
process initialization.

Specify a list of names and/or name=value pairs, separated by
whitespace or comma. Specify “{ name=value }” to protect whitespace
or comma in environment variable values (whitespace after the opening “{” and
before the closing “}”
is ignored). The form name=value is supported with Postfix version
2.1 and later; the use of {} is supported with Postfix 3.0 and
later.

Time to pause before accepting a new message, when the message
arrival rate exceeds the message delivery rate. This feature is
turned on by default (it’s disabled on SCO UNIX due to an SCO bug).

With the default 100 Postfix SMTP server process limit, “in_flow_delay
= 1s” limits the mail inflow to 100 messages per second above the
number of messages delivered per second.

Specify 0 to disable the feature. Valid delays are 0..10.

The local network interface addresses that this mail system receives
mail on. Specify “all” to receive mail on all network
interfaces (default), and “loopback-only” to receive mail
on loopback network interfaces only (Postfix version 2.2 and later). The
parameter also controls delivery of mail to user@[ip.address].

Note 1: you need to stop and start Postfix when this parameter changes.

Note 2: address information may be enclosed inside [],
but this form is not required here.

When inet_interfaces specifies just one IPv4 and/or IPv6 address
that is not a loopback address, the Postfix SMTP client will use
this address as the IP source address for outbound mail. Support
for IPv6 is available in Postfix version 2.2 and later.

On a multi-homed firewall with separate Postfix instances listening on the
“inside” and “outside” interfaces, this can prevent each instance from
being able to reach remote SMTP servers on the “other side” of the
firewall. Setting
smtp_bind_address to 0.0.0.0 avoids the potential problem for
IPv4, and setting smtp_bind_address6 to :: solves the problem
for IPv6.

A better solution for multi-homed firewalls is to leave inet_interfaces
at the default value and instead use explicit IP addresses in
the master.cf SMTP server definitions. This preserves the Postfix
SMTP client’s
loop detection, by ensuring that each side of the firewall knows that the
other IP address is still the same host. Setting $inet_interfaces to a
single IPv4 and/or IPV6 address is primarily useful with virtual
hosting of domains on
secondary IP addresses, when each IP address serves a different domain
(and has a different $myhostname setting).

See also the proxy_interfaces parameter, for network addresses that
are forwarded to Postfix by way of a proxy or address translator.

Examples:

inet_interfaces = all (DEFAULT)
inet_interfaces = loopback-only (Postfix version 2.2 and later)
inet_interfaces = 127.0.0.1
inet_interfaces = 127.0.0.1, [::1] (Postfix version 2.2 and later)
inet_interfaces = 192.168.1.2, 127.0.0.1

The Internet protocols Postfix will attempt to use when making
or accepting connections. Specify one or more of “ipv4”
or “ipv6”, separated by whitespace or commas. The form
“all” is equivalent to “ipv4, ipv6” or “ipv4”, depending
on whether the operating system implements IPv6.

With Postfix 2.8 and earlier the default is “ipv4”. For backwards
compatibility with these releases, the Postfix 2.9 and later upgrade
procedure appends an explicit “inet_protocols = ipv4″ setting to
main.cf when no explicit setting is present. This compatibility
workaround will be phased out as IPv6 deployment becomes more common.

This feature is available in Postfix 2.2 and later.

Note: you MUST stop and start Postfix after changing this
parameter.

On systems that pre-date IPV6_V6ONLY support (RFC 3493), an
IPv6 server will also accept IPv4 connections, even when IPv4 is
turned off with the inet_protocols parameter. On systems with
IPV6_V6ONLY support, Postfix will use separate server sockets for
IPv6 and IPv4, and each will accept only connections for the
corresponding protocol.

When IPv4 support is enabled via the inet_protocols parameter,
Postfix will look up DNS type A records, and will convert
IPv4-in-IPv6 client IP addresses (::ffff:1.2.3.4) to their original
IPv4 form (1.2.3.4). The latter is needed on hosts that pre-date
IPV6_V6ONLY support (RFC 3493).

When IPv6 support is enabled via the inet_protocols parameter,
Postfix will do DNS type AAAA record lookups.

When both IPv4 and IPv6 support are enabled, the Postfix SMTP
client will choose the protocol as specified with the
smtp_address_preference parameter. Postfix versions before 2.8
attempt to connect via IPv6 before attempting to use IPv4.

Examples:

inet_protocols = ipv4
inet_protocols = all (DEFAULT)
inet_protocols = ipv6
inet_protocols = ipv4, ipv6

The email address form that will be used in non-debug logging
(info, warning, etc.). As of Postfix 3.5 when an address localpart
contains spaces or other special characters, the localpart will be
quoted, for example:

    from=<"name with spaces"@example.com>

Older Postfix versions would log the internal (unquoted) form:

    from=<name with [email protected]>

The external and internal forms are identical for the vast
majority of email addresses that contain no spaces or other special
characters in the localpart.

The logging in external form is consistent with the address
form that Postfix 3.2 and later prefer for most table lookups. This
is therefore the more useful form for non-debug logging.

Specify “info_log_address_format = internal” for backwards
compatibility.

Postfix uses the unquoted form internally, because an attacker
can specify an email address in different forms by playing games
with quotes and backslashes. An attacker should not be able to use
such games to circumvent Postfix access policies.

This feature is available in Postfix 3.5 and later.

The initial per-destination concurrency level for parallel delivery
to the same destination.
With per-destination recipient limit > 1, a destination is a domain,
otherwise it is a recipient.

Use transport_initial_destination_concurrency to specify
a transport-specific override, where transport is the master.cf
name of the message delivery transport (Postfix 2.5 and later).

Warning: with concurrency of 1, one bad message can be enough to
block all mail to a site.

What categories of Postfix-generated mail are subject to
before-queue content inspection by non_smtpd_milters, header_checks
and body_checks. Specify zero or more of the following, separated
by whitespace or comma.

bounce

Inspect the content of delivery
status notifications.

notify

Inspect the content of postmaster
notifications by the smtp(8) and smtpd(8) processes.

NOTE: It’s generally not safe to enable content inspection of
Postfix-generated email messages. The user is warned.

This feature is available in Postfix 2.3 and later.

The numerical Postfix SMTP server response code when the client
HELO or EHLO command parameter is rejected by the reject_invalid_helo_hostname
restriction.

Do not change this unless you have a complete understanding of RFC 5321.

The time after which a client closes an idle internal communication
channel. The purpose is to allow Postfix daemon processes to
terminate voluntarily after they become idle. This is used, for
example, by the Postfix address resolving and rewriting clients.

With Postfix 2.4 the default value was reduced from 100s to 5s.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The time limit for sending or receiving information over an internal
communication channel. The purpose is to break out of deadlock
situations. If the time limit is exceeded the software aborts with a
fatal error.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The time after which a client closes an active internal communication
channel. The purpose is to allow Postfix daemon processes to
terminate voluntarily
after reaching their client limit. This is used, for example, by
the Postfix address resolving and rewriting clients.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.1 and later.

Optional setting that avoids lookups in the services(5) database.
This feature was implemented to address inconsistencies in the name
of the port “465” service. The ABNF is:

known_tcp_ports = empty | name-to-port *(“,” name-to-port)
name-to-port = 1*(service-name “=’) port-number

The comma is required. Whitespace is optional but it cannot appear
inside a service name or port number.

This feature is available in Postfix 3.6 and later.

Upon input, long lines are chopped up into pieces of at most
this length; upon delivery, long lines are reconstructed.

The initial OpenLDAP LMDB database size limit in bytes. Each time
a database becomes full, its size limit is doubled.

This feature is available in Postfix 2.11 and later.

The LMTP-specific version of the smtp_address_preference
configuration parameter. See there for details.

This feature is available in Postfix 2.8 and later.

The LMTP-specific version of the smtp_address_verify_target
configuration parameter. See there for details.

This feature is available in Postfix 3.0 and later.

When a remote LMTP server announces no DSN support, assume that
the
server performs final delivery, and send “delivered” delivery status
notifications instead of “relayed”. The default setting is backwards
compatible to avoid the infinitesimal possibility of breaking
existing LMTP-based content filters.

The LMTP-specific version of the smtp_balance_inet_protocols
configuration parameter. See there for details.

This feature is available in Postfix 3.3 and later.

The LMTP-specific version of the smtp_bind_address configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_bind_address6 configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_bind_address_enforce
configuration parameter. See there for details.

This feature is available in Postfix 3.7 and later.

The LMTP-specific version of the smtp_body_checks configuration
parameter. See there for details.

This feature is available in Postfix 2.5 and later.

Keep Postfix LMTP client connections open for up to $max_idle
seconds. When the LMTP client receives a request for the same
connection the connection is reused.

This parameter is available in Postfix version 2.2 and earlier.
With Postfix version 2.3 and later, see lmtp_connection_cache_on_demand,
lmtp_connection_cache_destinations, or lmtp_connection_reuse_time_limit.

The effectiveness of cached connections will be determined by the
number of remote LMTP servers in use, and the concurrency limit specified
for the Postfix LMTP client. Cached connections are closed under any of
the following conditions:

Most of these limitations have been with the Postfix
connection cache that is shared among multiple LMTP client
programs.

The LMTP-specific version of the smtp_cname_overrides_servername
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit). When no
connection can be made within the deadline, the LMTP client tries
the next address on the mail exchanger list.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

Example:

lmtp_connect_timeout = 30s

The LMTP-specific version of the smtp_connection_cache_destinations
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_connection_cache_on_demand
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the
smtp_connection_cache_time_limit configuration parameter.
See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_connection_reuse_count_limit
configuration parameter. See there for details.

This feature is available in Postfix 2.11 and later.

The LMTP-specific version of the smtp_connection_reuse_time_limit
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for sending the LMTP “.”,
and for receiving the remote LMTP server response. When no response
is received within the deadline, a warning is logged that the mail
may be delivered multiple times.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The Postfix LMTP client time limit for sending the LMTP DATA command,
and
for receiving the remote LMTP server response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The Postfix LMTP client time limit for sending the LMTP message
content.
When the connection stalls for more than $lmtp_data_xfer_timeout
the LMTP client terminates the transfer.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The LMTP-specific version of the smtp_defer_if_no_mx_address_found
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_delivery_status_filter
configuration parameter. See there for details.

This feature is available in Postfix 3.0 and later.

The maximal number of parallel deliveries to the same destination
via the lmtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the master.cf file.

The maximal number of recipients per message for the lmtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.

Setting this parameter to a value of 1 changes the meaning of
lmtp_destination_concurrency_limit from concurrency per domain into
concurrency per recipient.

Lookup tables, indexed by the remote LMTP server address, with
case insensitive lists of LHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix LMTP client will ignore in the LHLO
response
from a remote LMTP server. See lmtp_discard_lhlo_keywords for
details. The table is not indexed by hostname for consistency with
smtpd_discard_ehlo_keyword_address_maps.

This feature is available in Postfix 2.3 and later.

A case insensitive list of LHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix LMTP client will ignore in the LHLO
response
from a remote LMTP server.

This feature is available in Postfix 2.3 and later.

Notes:

Optional filter for Postfix LMTP client DNS lookup results.
See smtp_dns_reply_filter for details including an example.

This feature is available in Postfix 3.0 and later.

The LMTP-specific version of the smtp_dns_resolver_options
configuration parameter. See there for details.

This feature is available in Postfix 2.8 and later.

The LMTP-specific version of the smtp_dns_support_level
configuration parameter. See there for details.

This feature is available in Postfix 2.11 and later.

The LMTP-specific version of the smtp_enforce_tls configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

Optional list of relay hosts for LMTP destinations that can’t be
found or that are unreachable. In main.cf elements are separated by
whitespace or commas.

By default, mail is returned to the sender when a destination is not
found, and delivery is deferred when a destination is unreachable.

The fallback relays must be TCP destinations, specified without
a leading “inet:” prefix. Specify a host or host:port. Since MX
lookups do not apply with LMTP, there is no need to use the “[host]” or
“[host]:port” forms. If you specify multiple LMTP destinations, Postfix
will try them in the specified order.

This feature is available in Postfix 3.1 and later.

The LMTP-specific version of the smtp_generic_maps configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_header_checks configuration
parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_host_lookup configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The hostname to send in the LMTP LHLO command.

The default value is the machine hostname. Specify a hostname or
[ip.add.re.ss] or [ip:v6:add:re::ss].

This information can be specified in the main.cf file for all LMTP
clients, or it can be specified in the master.cf file for a specific
client, for example:

/etc/postfix/master.cf:
    mylmtp ... lmtp -o lmtp_lhlo_name=foo.bar.com

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for sending the LHLO command,
and for receiving the initial remote LMTP server response.

Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds).

The LMTP-specific version of the smtp_line_length_limit
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for sending the MAIL FROM command,
and for receiving the remote LMTP server response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The LMTP-specific version of the smtp_mime_header_checks
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_min_data_rate configuration
parameter. See there for details.

This feature is available in Postfix 3.7 and later.

The LMTP-specific version of the smtp_mx_address_limit configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_mx_session_limit configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_nested_header_checks
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_per_record_deadline
configuration parameter. See there for details.

This feature is available in Postfix 2.9 and later.

The LMTP-specific version of the smtp_per_request_deadline
configuration parameter. See there for details.

This feature is available in Postfix 3.7 and later.

The LMTP-specific version of the smtp_pix_workaround_delay_time
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_pix_workaround_maps
configuration parameter. See there for details.

This feature is available in Postfix 2.4 and later.

The LMTP-specific version of the smtp_pix_workaround_threshold_time
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_pix_workaround
configuration parameter. See there for details.

This feature is available in Postfix 2.4 and later.

The Postfix LMTP client time limit for sending the QUIT command,
and for receiving the remote LMTP server response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The LMTP-specific version of the smtp_quote_rfc821_envelope
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_randomize_addresses
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for sending the RCPT TO command,
and for receiving the remote LMTP server response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The LMTP-specific version of the smtp_reply_filter
configuration parameter. See there for details.

This feature is available in Postfix 2.7 and later.

The Postfix LMTP client time limit for sending the RSET command,
and for receiving the remote LMTP server response. The LMTP client
sends RSET in
order to finish a recipient address probe, or to verify that a
cached connection is still alive.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The LMTP-specific version of the smtp_sasl_auth_cache_name
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_sasl_auth_cache_time
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

Enable SASL authentication in the Postfix LMTP client.

The LMTP-specific version of the smtp_sasl_auth_soft_bounce
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_sasl_mechanism_filter
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

Optional Postfix LMTP client lookup tables with one username:password entry
per host or domain. If a remote host or domain has no username:password
entry, then the Postfix LMTP client will not attempt to authenticate
to the remote host.

Implementation-specific information that is passed through to
the SASL plug-in implementation that is selected with
lmtp_sasl_type. Typically this specifies the name of a
configuration file or rendezvous point.

This feature is available in Postfix 2.3 and later.

SASL security options; as of Postfix 2.3 the list of available
features depends on the SASL client implementation that is selected
with lmtp_sasl_type.

The following security features are defined for the cyrus
client SASL implementation:

noplaintext

Disallow authentication methods that use plaintext passwords.

noactive

Disallow authentication methods that are vulnerable to non-dictionary
active attacks.

nodictionary

Disallow authentication methods that are vulnerable to passive
dictionary attacks.

noanonymous

Disallow anonymous logins.

Example:

lmtp_sasl_security_options = noplaintext

The LMTP-specific version of the smtp_sasl_tls_security_options
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the
smtp_sasl_tls_verified_security_options configuration parameter.
See there for details.

This feature is available in Postfix 2.3 and later.

The SASL plug-in type that the Postfix LMTP client should use
for authentication. The available types are listed with the
“postconf -A” command.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_send_dummy_mail_auth
configuration parameter. See there for details.

This feature is available in Postfix 2.9 and later.

Send an XFORWARD command to the remote LMTP server when the LMTP LHLO
server response announces XFORWARD support. This allows an lmtp(8)
delivery agent, used for content filter message injection, to
forward the name, address, protocol and HELO name of the original
client to the content filter and downstream LMTP server.
Before you change the value to yes, it is best to make sure that
your content filter supports this command.

This feature is available in Postfix 2.1 and later.

The LMTP-specific version of the smtp_sender_dependent_authentication
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_skip_5xx_greeting
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

Wait for the response to the LMTP QUIT command.

The LMTP-specific version of the smtp_starttls_timeout configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The default TCP port that the Postfix LMTP client connects to.
Specify a symbolic name (see services(5)) or a numeric port.

The LMTP-specific version of the smtp_tls_CAfile
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_CApath
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_block_early_mail_reply
configuration parameter. See there for details.

This feature is available in Postfix 2.7 and later.

The LMTP-specific version of the smtp_tls_cert_file
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_chain_files configuration
parameter. See there for details.

This feature is available in Postfix 3.4 and later.

The LMTP-specific version of the smtp_tls_ciphers configuration
parameter. See there for details.

This feature is available in Postfix 2.6 and later.

The LMTP-specific version of the smtp_tls_connection_reuse configuration
parameter. See there for details.

This feature is available in Postfix 3.4 and later.

The LMTP-specific version of the smtp_tls_dcert_file
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_dkey_file
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_eccert_file configuration
parameter. See there for details.

This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later.

The LMTP-specific version of the smtp_tls_eckey_file configuration
parameter. See there for details.

This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later.

The LMTP-specific version of the smtp_tls_enforce_peername
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_exclude_ciphers
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_fingerprint_cert_match
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_tls_fingerprint_digest
configuration parameter. See there for details.

This feature is available in Postfix 2.5 and later.

The LMTP-specific version of the smtp_tls_force_insecure_host_tlsa_lookup
configuration parameter. See there for details.

This feature is available in Postfix 2.11 and later.

The LMTP-specific version of the smtp_tls_key_file
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_loglevel
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_mandatory_ciphers
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_mandatory_exclude_ciphers
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_mandatory_protocols
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_note_starttls_offer
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_per_site configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_policy_maps
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_protocols configuration
parameter. See there for details.

This feature is available in Postfix 2.6 and later.

The LMTP-specific version of the smtp_tls_scert_verifydepth
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_secure_cert_match
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_security_level configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_servername configuration
parameter. See there for details.

This feature is available in Postfix 3.4 and later.

The LMTP-specific version of the smtp_tls_session_cache_database
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_session_cache_timeout
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_trust_anchor_file
configuration parameter. See there for details.

This feature is available in Postfix 2.11 and later.

The LMTP-specific version of the smtp_tls_verify_cert_match
configuration parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The LMTP-specific version of the smtp_tls_wrappermode configuration
parameter. See there for details.

This feature is available in Postfix 3.0 and later.

The LMTP-specific version of the smtp_use_tls configuration
parameter. See there for details.

This feature is available in Postfix 2.3 and later.

The Postfix LMTP client time limit for sending the XFORWARD command,
and for receiving the remote LMTP server response.

In case of problems the client does NOT try the next address on
the mail exchanger list.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.1 and later.

Optional shell program for local(8) delivery to non-Postfix commands.
By default, non-Postfix commands are executed directly; commands
are given to the default shell (typically, /bin/sh) only when they
contain shell meta characters or shell built-in commands.

“sendmail’s restricted shell” (smrsh) is what most people will
use in order to restrict what programs can be run from e.g. .forward
files (smrsh is part of the Sendmail distribution).

Note: when a shell program is specified, it is invoked even
when the command contains no shell built-in commands or meta
characters.

Example:

local_command_shell = /some/where/smrsh -c
local_command_shell = /bin/bash -c

Optional filter for the local(8) delivery agent to change the
status code or explanatory text of successful or unsuccessful
deliveries. See default_delivery_status_filter for details.

This feature is available in Postfix 3.0 and later.

The maximal number of parallel deliveries via the local mail
delivery transport to the same recipient (when
“local_destination_recipient_limit = 1″) or the maximal number of
parallel deliveries to the same local domain (when
“local_destination_recipient_limit > 1″). This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the master.cf file.

A low limit of 2 is recommended, just in case someone has an
expensive shell command in a .forward file or in an alias (e.g.,
a mailing list manager). You don’t want to run lots of those at
the same time.

The maximal number of recipients per message delivery via the
local mail delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.

Setting this parameter to a value > 1 changes the meaning of
local_destination_concurrency_limit from concurrency per recipient
into concurrency per domain.

Rewrite message header addresses in mail from these clients and
update incomplete addresses with the domain name in $myorigin or
$mydomain; either don’t rewrite message headers from other clients
at all, or rewrite message headers and update incomplete addresses
with the domain specified in the remote_header_rewrite_domain
parameter.

See the append_at_myorigin and append_dot_mydomain parameters
for details of how domain names are appended to incomplete addresses.

Specify a list of zero or more of the following:

permit_inet_interfaces

Append the domain name in $myorigin or $mydomain when the
client IP address matches $inet_interfaces. This is enabled by
default.

permit_mynetworks

Append the domain name in $myorigin or $mydomain when the
client IP address matches any network or network address listed in
$mynetworks. This setting will not prevent remote mail header
address rewriting when mail from a remote client is forwarded by
a neighboring system.

permit_sasl_authenticated

Append the domain name in $myorigin or $mydomain when the
client is successfully authenticated via the RFC 4954 (AUTH)
protocol.

permit_tls_clientcerts

Append the domain name in $myorigin or $mydomain when the
remote SMTP client TLS certificate fingerprint or public key fingerprint
(Postfix 2.9 and later) is listed in $relay_clientcerts.
The fingerprint digest algorithm is configurable via the
smtpd_tls_fingerprint_digest parameter (hard-coded as md5 prior to
Postfix version 2.5).

The default algorithm is sha256 with Postfix ≥ 3.6
and the compatibility_level set to 3.6 or higher. With Postfix
≤ 3.5, the default algorithm is md5. The best-practice
algorithm is now sha256. Recent advances in hash function
cryptanalysis have led to md5 and sha1 being deprecated in favor of
sha256. However, as long as there are no known “second pre-image”
attacks against the older algorithms, their use in this context, though
not recommended, is still likely safe.

permit_tls_all_clientcerts

Append the domain name in $myorigin or $mydomain when the
remote SMTP client TLS certificate is successfully verified, regardless of
whether it is listed on the server, and regardless of the certifying
authority.

type:table

type:table

Append the domain name in $myorigin or $mydomain when the
client IP address matches the specified lookup table.
The lookup result is ignored, and no subnet lookup is done. This
is suitable for, e.g., pop-before-smtp lookup tables.

Examples:

The Postfix < 2.2 backwards compatible setting: always rewrite
message headers, and always append my own domain to incomplete
header addresses.

local_header_rewrite_clients = static:all

The purist (and default) setting: rewrite headers only in mail
from Postfix sendmail and in SMTP mail from this machine.

local_header_rewrite_clients = permit_inet_interfaces

The intermediate setting: rewrite header addresses and append
$myorigin or $mydomain information only with mail from Postfix
sendmail, from local clients, or from authorized SMTP clients.

Note: this setting will not prevent remote mail header address
rewriting when mail from a remote client is forwarded by a neighboring
system.

local_header_rewrite_clients = permit_mynetworks,
    permit_sasl_authenticatedpermit_tls_clientcertscheck_address_maphash:/etc/postfix/pop-before-smtp

A list of lookup tables that are searched by the UNIX login name,
and that return a list of allowed envelope sender patterns separated
by space or comma. These sender patterns are enforced by the Postfix
postdrop(1) command. The default is backwards-compatible:
every user may specify any sender envelope address.

When no UNIX login name is available, the postdrop(1) command will
prepend “uid:” to the numerical UID and use that instead.

This feature ignores address extensions in the user-specified
envelope sender address.

The following sender patterns are special; these cannot be used
as part of a longer pattern.

*

This pattern allows any envelope sender address.

<>

This pattern allows the empty
envelope sender address. See the
empty_address_local_login_sender_maps_lookup_key configuration
parameter.

@domain

This pattern allows an
envelope sender address when the ‘@‘ and domain part
match.

Examples:

/etc/postfix/main.cf:
    # Allow root and postfix full control, anyone else can only
    # send mail as themselves. Use "uid:" followed by the numerical
    # UID when the UID has no entry in the UNIX password file.
    local_login_sender_maps =
        inline:{ { root = * }, { postfix = * } },
        pcre:/etc/postfix/login_senders

/etc/postfix/login_senders:
   # Allow both the bare username and the user@domain forms.
    /(. )/ $1 [email protected]

This feature is available in Postfix 3.6 and later.

Lookup tables with all names or addresses of local recipients:
a recipient address is local when its domain matches $mydestination,
$inet_interfaces or $proxy_interfaces. Specify @domain as a
wild-card for domains that do not have a valid recipient list.
Technically, tables listed with $local_recipient_maps are used as
lists: Postfix needs to know only if a lookup string is found or
not, but it does not use the result from table lookup.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

If this parameter is non-empty (the default), then the Postfix SMTP
server will reject mail for unknown local users.

To turn off local recipient checking in the Postfix SMTP server,
specify “local_recipient_maps =” (i.e. empty).

The default setting assumes that you use the default Postfix local
delivery agent for local delivery. You need to update the
local_recipient_maps setting if:

Details are described in the LOCAL_RECIPIENT_README file.

Beware: if the Postfix SMTP server runs chrooted, you need to access
the passwd file via the proxymap(8) service, in order to overcome
chroot access restrictions. The alternative, maintaining a copy of
the system password file in the chroot jail is not practical.

Examples:

local_recipient_maps =

The default mail delivery transport and next-hop destination
for final delivery to domains listed with mydestination, and for
[ipaddress] destinations that match $inet_interfaces or $proxy_interfaces.
This information can be overruled with the transport(5) table.

By default, local mail is delivered to the transport called “local”,
which is just the name of a service that is defined the master.cf file.

Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in master.cf.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent.

Beware: if you override the default local delivery agent then you
need to review the LOCAL_RECIPIENT_README document, otherwise the
SMTP server may reject mail for local recipients.

Optional catch-all destination for unknown local(8) recipients.
By default, mail for unknown recipients in domains that match
$mydestination, $inet_interfaces or $proxy_interfaces is returned
as undeliverable.

The luser_relay value is not subject to Postfix configuration
parameter $name expansion. Instead, the following $name expansions
are done:

$domain

The recipient domain.

$extension

The recipient address extension.

$home

The recipient’s home directory.

$local

The entire recipient address localpart.

$recipient

The full recipient address.

$recipient_delimiter

The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier).

$shell

The recipient’s login shell.

$user

The recipient username.

${name?value}

${name?{value}} (Postfix ≥ 3.0)

Expands to value when $name is non-empty.

${name:value}

${name:{value}} (Postfix ≥ 3.0)

Expands to value when $name is empty.

${name?{value1}:{value2}} (Postfix ≥ 3.0)

Expands to value1 when $name is non-empty,
value2 otherwise.

Instead of $name you can also specify ${name} or $(name).

Note: luser_relay works only for the Postfix local(8) delivery agent.

Note: if you use this feature for accounts not in the UNIX password
file, then you must specify “local_recipient_maps =” (i.e. empty)
in the main.cf file, otherwise the Postfix SMTP server will reject mail
for non-UNIX accounts with “User unknown in local recipient table”.

Examples:

luser_relay = [email protected]
luser_relay = [email protected]
luser_relay = admin $local

The mail system name that is displayed in Received: headers, in
the SMTP greeting banner, and in bounced mail.

The UNIX system account that owns the Postfix queue and most Postfix
daemon processes. Specify the name of an unprivileged user account
that does not share a user or group ID with other accounts, and that
owns no other files
or processes on the system. In particular, don’t specify nobody
or daemon. PLEASE USE A DEDICATED USER ID AND GROUP ID.

When this parameter value is changed you need to re-run “postfix
set-permissions” (with Postfix version 2.0 and earlier:
“/etc/postfix/post-install set-permissions“.

The Postfix release date, in “YYYYMMDD” format.

The directory where local(8) UNIX-style mailboxes are kept. The
default setting depends on the system type. Specify a name ending
in / for maildir-style delivery.

Note: maildir delivery is done with the privileges of the recipient.
If you use the mail_spool_directory setting for maildir style
delivery, then you must create the top-level maildir directory in
advance. Postfix will not create it.

Examples:

mail_spool_directory = /var/mail
mail_spool_directory = /var/spool/mail

The version of the mail system. Stable releases are named
major.minor.patchlevel. Experimental releases
also include the release date. The version string can be used in,
for example, the SMTP greeting banner.

Optional external command that the local(8) delivery agent should
use for mailbox delivery. The command is run with the user ID and
the primary group ID privileges of the recipient. Exception:
command delivery for root executes with $default_privs privileges.
This is not a problem, because 1) mail for root should always be
aliased to a real user and 2) don’t log in as root, use “su” instead.

The following environment variables are exported to the command:

CLIENT_ADDRESS

Remote client network address. Available in Postfix version 2.2 and
later.

CLIENT_HELO

Remote client EHLO command parameter. Available in Postfix version 2.2
and later.

CLIENT_HOSTNAME

Remote client hostname. Available in Postfix version 2.2 and later.

CLIENT_PROTOCOL

Remote client protocol. Available in Postfix version 2.2 and later.

DOMAIN

The domain part of the recipient address.

EXTENSION

The optional address extension.

HOME

The recipient home directory.

LOCAL

The recipient address localpart.

LOGNAME

The recipient’s username.

ORIGINAL_RECIPIENT

The entire recipient address, before any address rewriting or
aliasing.

RECIPIENT

The full recipient address.

SASL_METHOD

SASL authentication method specified in the remote client AUTH
command. Available in Postfix version 2.2 and later.

SASL_SENDER

SASL sender address specified in the remote client MAIL FROM
command. Available in Postfix version 2.2 and later.

SASL_USER

SASL username specified in the remote client AUTH command.
Available in Postfix version 2.2 and later.

SENDER

The full sender address.

SHELL

The recipient’s login shell.

USER

The recipient username.

Unlike other Postfix configuration parameters, the mailbox_command
parameter is not subjected to $name substitutions. This is to make
it easier to specify shell syntax (see example below).

If you can, avoid shell meta characters because they will force
Postfix to run an expensive shell process. If you’re delivering
via “procmail” then running a shell won’t make a noticeable difference
in the total cost.

Note: if you use the mailbox_command feature to deliver mail
system-wide, you must set up an alias that forwards mail for root
to a real user.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Examples:

mailbox_command = /some/where/procmail
mailbox_command = /some/where/procmail -a "$EXTENSION"
mailbox_command = /some/where/maildrop -d "$USER"
        -f "$SENDER" "$EXTENSION"

Optional lookup tables with per-recipient external commands to use
for local(8) mailbox delivery. Behavior is as with mailbox_command.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

How to lock a UNIX-style local(8) mailbox before attempting delivery.
For a list of available file locking methods, use the “postconf
-l” command.

This setting is ignored with maildir style delivery,
because such deliveries are safe without explicit locks.

Note: The dotlock method requires that the recipient UID or
GID has write access to the parent directory of the mailbox file.

Note: the default setting of this parameter is system dependent.

The maximal size of any local(8) individual mailbox or maildir
file, or zero (no limit). In fact, this limits the size of any
file that is written to upon local delivery, including files written
by external commands that are executed by the local(8) delivery
agent. The value cannot exceed LONG_MAX (typically, a 32-bit or
64-bit signed integer).

This limit must not be smaller than the message size limit.

Optional message delivery transport that the local(8) delivery
agent should use for mailbox delivery to all local recipients,
whether or not they are found in the UNIX passwd database.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Optional lookup tables with per-recipient message delivery
transports to use for local(8) mailbox delivery, whether or not the
recipients are found in the UNIX passwd database.

The precedence of local(8) delivery features from high to low
is: aliases, .forward files, mailbox_transport_maps, mailbox_transport,
mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory,
fallback_transport_maps, fallback_transport and luser_relay.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

For safety reasons, this feature does not allow $number
substitutions in regular expression maps.

This feature is available in Postfix 2.3 and later.

The name of an optional logfile that is written by the Postfix
postlogd(8) service. An empty value selects logging to syslogd(8).
Specify “/dev/stdout” to select logging to standard output. Stdout
logging requires that Postfix is started with “postfix start-fg”.

Note 1: The maillog_file parameter value must contain a prefix
that is specified with the maillog_file_prefixes parameter.

Note 2: Some Postfix non-daemon programs may still log information
to syslogd(8), before they have processed their configuration
parameters and command-line options.

This feature is available in Postfix 3.4 and later.

The program to run after rotating $maillog_file with “postfix
logrotate”. The command is run with the rotated logfile name as its
first argument.

This feature is available in Postfix 3.4 and later.

A list of allowed prefixes for a maillog_file value. This is a
safety feature to contain the damage from a single configuration
mistake. Specify one or more prefix strings, separated by comma or
whitespace.

This feature is available in Postfix 3.4 and later.

The format of the suffix to append to $maillog_file while rotating
the file with “postfix logrotate”. See strftime(3) for syntax. The
default suffix, YYYYMMDD-HHMMSS, allows logs to be rotated frequently.

This feature is available in Postfix 3.4 and later.

Sendmail compatibility feature that specifies where the Postfix
mailq(1) command is installed. This command can be used to
list the Postfix mail queue.

Where the Postfix manual pages are installed.

Obsolete feature: use the reject_rbl_client feature instead.

The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the reject_rbl_client, reject_rhsbl_client,
reject_rhsbl_reverse_client, reject_rhsbl_sender or
reject_rhsbl_recipient restriction.

Do not change this unless you have a complete understanding of RFC 5321.

What addresses are subject to address masquerading.

By default, address masquerading is limited to envelope sender
addresses, and to header sender and header recipient addresses.
This allows you to use address masquerading on a mail gateway while
still being able to forward mail to users on individual machines.

Specify zero or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient

Optional list of domains whose subdomain structure will be stripped
off in email addresses.

The list is processed left to right, and processing stops at the
first match. Thus,

masquerade_domains = foo.example.com example.com

strips “[email protected]” to “[email protected]”,
but strips “[email protected]” to “[email protected]”.

A domain name prefixed with ! means do not masquerade this domain
or its subdomains. Thus,

masquerade_domains = !foo.example.com example.com

does not change “[email protected]” or “[email protected]”,
but strips “[email protected]” to “[email protected]”.

Note: with Postfix version 2.2, message header address masquerading
happens only when message header address rewriting is enabled:

To get the behavior before Postfix version 2.2, specify
“local_header_rewrite_clients = static:all”.

Example:

masquerade_domains = $mydomain

Optional list of user names that are not subjected to address
masquerading, even when their addresses match $masquerade_domains.

By default, address masquerading makes no exceptions.

Specify a list of user names, “/file/name” or “type:table” patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A “/file/name”
pattern is replaced
by its contents; a “type:table” lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify “!pattern”
to exclude a name from the list. The form “!/file/name” is supported
only in Postfix version 2.4 and later.

Examples:

masquerade_exceptions = root, mailer-daemon
masquerade_exceptions = root

Selectively disable master(8) listener ports by service type
or by service name and type. Specify a list of service types
(“inet”, “unix”, “fifo”, or “pass”) or “name/type” tuples, where
“name” is the first field of a master.cf entry and “type” is a
service type. As with other Postfix matchlists, a search stops at
the first match. Specify “!pattern” to exclude a service from the
list. By default, all master(8) listener ports are enabled.

Note: this feature does not support “/file/name” or “type:table”
patterns, nor does it support wildcards such as “*” or “all”. This
is intentional.

Examples:

# With Postfix 2.6..2.10 use '.' instead of '/'.
# Turn on all master(8) listener ports (the default).
master_service_disable =
# Turn off only the main SMTP listener port.
master_service_disable = smtp/inet
# Turn off all TCP/IP listener ports.
master_service_disable = inet
# Turn off all TCP/IP listener ports except "foo".
master_service_disable = !foo/inet, inet

This feature is available in Postfix 2.6 and later.

The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily. This
parameter
is ignored by the Postfix queue manager and by other long-lived
Postfix daemon processes.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily. This parameter
is ignored by the Postfix queue
manager and by other long-lived Postfix daemon processes.

The maximal time between attempts to deliver a deferred message.

This parameter should be set to a value greater than or equal
to $minimal_backoff_time. See also $queue_run_delay.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

Consider a message as undeliverable, when delivery fails with a
temporary error, and the time in the queue has reached the
maximal_queue_lifetime limit.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

Specify 0 when mail delivery should be tried only once.

Names of message headers that the cleanup(8) daemon will remove
after applying header_checks(5) and before invoking Milter applications.
The default setting is compatible with Postfix < 3.0.

Specify a list of header names, separated by comma or space.
Names are matched in a case-insensitive manner. The list of supported
header names is limited only by available memory.

This feature is available in Postfix 3.0 and later.

The set of characters that Postfix will reject in message
content. The usual C-like escape sequences are recognized: a
b f n r t v ddd (up to three octal digits) and
\.

Note 1: this feature does not recognize text that requires MIME
decoding. It inspects raw message content, just like header_checks
and body_checks.

Note 2: this feature is disabled with “receive_override_options
= no_header_body_checks“.

Example:

message_reject_characters = 

This feature is available in Postfix 2.3 and later.

The maximal size in bytes of a message, including envelope information.
The value cannot exceed LONG_MAX (typically, a 32-bit or 64-bit
signed integer).

Note: be careful when making changes. Excessively small values
will result in the loss of non-delivery notifications, when a bounce
message size exceeds the local or remote MTA’s message size limit.

The set of characters that Postfix will remove from message
content. The usual C-like escape sequences are recognized: a
b f n r t v ddd (up to three octal digits) and
\.

Note 1: this feature does not recognize text that requires MIME
decoding. It inspects raw message content, just like header_checks
and body_checks.

Note 2: this feature is disabled with “receive_override_options
= no_header_body_checks“.

Example:

message_strip_characters = 

This feature is available in Postfix 2.3 and later.

The location of non-executable files that are shared among
multiple Postfix instances, such as postfix-files, dynamicmaps.cf,
and the multi-instance template files main.cf.proto and master.cf.proto.
This directory should contain only Postfix-related files. Typically,
the meta_directory parameter has the same default as the config_directory
parameter (/etc/postfix or /usr/local/etc/postfix).

For backwards compatibility with Postfix versions 2.6..2.11,
specify “meta_directory = $daemon_directory” in main.cf before
installing or upgrading Postfix, or specify “meta_directory =
/path/name” on the “make makefiles”, “make install” or “make upgrade”
command line.

This feature is available in Postfix 3.0 and later.

The time limit for sending an SMTP command to a Milter (mail
filter) application, and for receiving the response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.3 and later.

The macros that are sent to Milter (mail filter) applications
after completion of an SMTP connection. See MILTER_README
for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The time limit for connecting to a Milter (mail filter)
application, and for negotiating protocol options.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.3 and later.

The time limit for sending message content to a Milter (mail
filter) application, and for receiving the response.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.3 and later.

The macros that are sent to version 4 or higher Milter (mail
filter) applications after the SMTP DATA command. See MILTER_README
for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The default action when a Milter (mail filter) response is
unavailable (for example, bad Postfix configuration or Milter
failure). Specify one of the following:

accept

Proceed as if the mail filter was not present.

reject

Reject all further commands in this session
with a permanent status code.

tempfail

Reject all further commands in this session
with a temporary status code.

quarantine

Like “accept”, but freeze the message in
the “hold” queue. Available with Postfix 2.6 and later.

This feature is available in Postfix 2.3 and later.

The macros that are sent to Milter (mail filter) applications
after the message end-of-data. See MILTER_README for a list of
available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The macros that are sent to Milter (mail filter) applications
after the end of the message header. See MILTER_README for a list
of available macro names and their meanings.

This feature is available in Postfix 2.5 and later.

Optional lookup tables for content inspection of message headers
that are produced by Milter applications. See the header_checks(5)
manual page available actions. Currently, PREPEND is not implemented.

The following example sends all mail that is marked as SPAM to
a spam handling machine. Note that matches are case-insensitive
by default.

/etc/postfix/main.cf:
    milter_header_checks = pcre:/etc/postfix/milter_header_checks

/etc/postfix/milter_header_checks:
    /^X-SPAM-FLAG:s YES/ FILTER mysmtp:sanitizer.example.com:25

The milter_header_checks mechanism could also be used for
allowlisting. For example it could be used to skip heavy content
inspection for DKIM-signed mail from known friendly domains.

This feature is available in Postfix 2.7, and as an optional
patch for Postfix 2.6.

The macros that are sent to Milter (mail filter) applications
after the SMTP HELO or EHLO command. See
MILTER_README for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The {daemon_name} macro value for Milter (mail filter) applications.
See MILTER_README for a list of available macro names and their
meanings.

This feature is available in Postfix 2.3 and later.

Optional list of name=value pairs that specify default
values for arbitrary macros that Postfix may send to Milter
applications. These defaults are used when there is no corresponding
information from the message delivery context.

Specify name=value or {name=value} pairs separated
by comma or whitespace. Enclose a pair in “{}” when a value contains
comma or whitespace (this form ignores whitespace after the enclosing
“{“, around the “=”, and before the enclosing “}”).

This feature is available in Postfix 3.1 and later.

The {v} macro value for Milter (mail filter) applications.
See MILTER_README for a list of available macro names and their
meanings.

This feature is available in Postfix 2.3 and later.

The macros that are sent to Milter (mail filter) applications
after the SMTP MAIL FROM command. See MILTER_README
for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The mail filter protocol version and optional protocol extensions
for communication with a Milter application; prior to Postfix 2.6
the default protocol is 2. Postfix
sends this version number during the initial protocol handshake.
It should match the version number that is expected by the mail
filter application (or by its Milter library).

Protocol versions:

2

Use Sendmail 8 mail filter protocol version 2 (default
with Sendmail version 8.11 .. 8.13 and Postfix version 2.3 ..
2.5).

3

Use Sendmail 8 mail filter protocol version 3.

4

Use Sendmail 8 mail filter protocol version 4.

6

Use Sendmail 8 mail filter protocol version 6 (default
with Sendmail version 8.14 and Postfix version 2.6).

Protocol extensions:

no_header_reply

Specify this when the Milter application
will not reply for each individual message header.

This feature is available in Postfix 2.3 and later.

The macros that are sent to Milter (mail filter) applications
after the SMTP RCPT TO command. See MILTER_README
for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The macros that are sent to version 3 or higher Milter (mail
filter) applications after an unknown SMTP command. See MILTER_README
for a list of available macro names and their meanings.

This feature is available in Postfix 2.3 and later.

The maximal length of MIME multipart boundary strings. The MIME
processor is unable to distinguish between boundary strings that
do not differ in the first $mime_boundary_length_limit characters.

This feature is available in Postfix 2.0 and later.

Optional lookup tables for content inspection of MIME related
message headers, as described in the header_checks(5) manual page.

This feature is available in Postfix 2.0 and later.

The maximal recursion level that the MIME processor will handle.
Postfix refuses mail that is nested deeper than the specified limit.

This feature is available in Postfix 2.0 and later.

The minimal time between attempts to deliver a deferred message;
prior to Postfix 2.4 the default value was 1000s.

This parameter also limits the time an unreachable destination is
kept in the short-term, in-memory, destination status cache.

This parameter should be set greater than or equal to
$queue_run_delay. See also $maximal_backoff_time.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

An optional list of non-default Postfix configuration directories;
these directories belong to additional Postfix instances that share
the Postfix executable files and documentation with the default
Postfix instance, and that are started, stopped, etc., together
with the default Postfix instance. Specify a list of pathnames
separated by comma or whitespace.

When $multi_instance_directories is empty, the postfix(1) command
runs in single-instance mode and operates on a single Postfix
instance only. Otherwise, the postfix(1) command runs in multi-instance
mode and invokes the multi-instance manager specified with the
multi_instance_wrapper parameter. The multi-instance manager in
turn executes postfix(1) commands for the default instance and for
all Postfix instances in $multi_instance_directories.

Currently, this parameter setting is ignored except for the
default main.cf file.

This feature is available in Postfix 2.6 and later.

Allow this Postfix instance to be started, stopped, etc., by a
multi-instance manager. By default, new instances are created in
a safe state that prevents them from being started inadvertently.
This parameter is reserved for the multi-instance manager.

This feature is available in Postfix 2.6 and later.

The optional instance group name of this Postfix instance. A
group identifies closely-related Postfix instances that the
multi-instance manager can start, stop, etc., as a unit. This
parameter is reserved for the multi-instance manager.

This feature is available in Postfix 2.6 and later.

The optional instance name of this Postfix instance. This name
becomes also the default value for the syslog_name parameter.

This feature is available in Postfix 2.6 and later.

The pathname of a multi-instance manager command that the
postfix(1) command invokes when the multi_instance_directories
parameter value is non-empty. The pathname may be followed by
initial command arguments separated by whitespace; shell
metacharacters such as quotes are not supported in this context.

The postfix(1) command invokes the manager command with the
postfix(1) non-option command arguments on the manager command line,
and with all installation configuration parameters exported into
the manager command process environment. The manager command in
turn invokes the postfix(1) command for individual Postfix instances
as “postfix -c config_directorycommand“.

This feature is available in Postfix 2.6 and later.

The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the reject_multi_recipient_bounce
restriction.

Do not change this unless you have a complete understanding of RFC 5321.

This feature is available in Postfix 2.1 and later.

The list of domains that are delivered via the $local_transport
mail delivery transport. By default this is the Postfix local(8)
delivery agent which looks up all recipients in /etc/passwd and
/etc/aliases. The SMTP server validates recipient addresses with
$local_recipient_maps and rejects non-existent recipients. See also
the local domain class in the ADDRESS_CLASS_README file.

The default mydestination value specifies names for the local
machine only. On a mail domain gateway, you should also include
$mydomain.

The $local_transport delivery method is also selected for mail
addressed to user@[the.net.work.address] of the mail system (the
IP addresses specified with the inet_interfaces and proxy_interfaces
parameters).

Warnings:

Specify a list of host or domain names, “/file/name” or “type:table”
patterns, separated by commas and/or whitespace. A “/file/name”
pattern is replaced by its contents; a “type:table” lookup table
is matched when a name matches a lookup key (the lookup result is
ignored). Continue long lines by starting the next line with
whitespace.

Examples:

mydestination = $myhostname, localhost.$mydomain $mydomainmydestination = $myhostname, localhost.$mydomain www.$mydomain, ftp.$mydomain

The internet domain name of this mail system. The default is to
use $myhostname minus the first component, or “localdomain” (Postfix
2.3 and later). $mydomain is used as
a default value for many other configuration parameters.

Example:

mydomain = domain.tld

The internet hostname of this mail system. The default is to use
the fully-qualified domain name (FQDN) from gethostname(), or to
use the non-FQDN result from gethostname() and append “.$mydomain“.
$myhostname is used as a default value for many other configuration
parameters.

Example:

myhostname = host.example.com

The list of “trusted” remote SMTP clients that have more privileges than
“strangers”.

In particular, “trusted” SMTP clients are allowed to relay mail
through Postfix. See the smtpd_relay_restrictions parameter
description in the postconf(5) manual.

You can specify the list of “trusted” network addresses by hand
or you can let Postfix do it for you (which is the default).
See the description of the mynetworks_style parameter for more
information.

If you specify the mynetworks list by hand,
Postfix ignores the mynetworks_style setting.

Specify a list of network addresses or network/netmask patterns,
separated by commas and/or whitespace. Continue long lines by
starting the next line with whitespace.

The netmask specifies the number of bits in the network part
of a host address. You can also specify “/file/name” or “type:table”
patterns. A “/file/name” pattern is replaced by its contents; a
“type:table” lookup table is matched when a table entry matches a
lookup string (the lookup result is ignored).

The list is matched left to right, and the search stops on the
first match. Specify “!pattern” to exclude an address or network
block from the list. The form “!/file/name” is supported only
in Postfix version 2.4 and later.

Note 1: Pattern matching of domain names is controlled by the
presence or absence of “mynetworks” in the parent_domain_matches_subdomains
parameter value.

Note 2: IP version 6 address information must be specified inside
[] in the mynetworks value, and in files specified with
“/file/name”. IP version 6 addresses contain the “:” character,
and would otherwise be confused with a “type:table” pattern.

Note 3: CIDR ranges cannot be specified in hash tables. Use cidr
tables if CIDR ranges are used.

Examples:

mynetworks = 127.0.0.0/8 168.100.189.0/28
mynetworks = !192.168.0.1, 192.168.0.0/28
mynetworks = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
mynetworks = $config_directory/mynetworks
mynetworks = hash:/etc/postfix/network_table
mynetworks = cidr:/etc/postfix/network_table.cidr

The method to generate the default value for the mynetworks parameter.
This is the list of trusted networks for relay access control etc.

The domain name that locally-posted mail appears to come
from, and that locally posted mail is delivered to. The default,
$myhostname, is adequate for small sites. If you run a domain with
multiple machines, you should (1) change this to $mydomain and (2)
set up a domain-wide alias database that aliases each user to
[email protected].

Example:

myorigin = $mydomain

Optional lookup tables for content inspection of non-MIME message
headers in attached messages, as described in the header_checks(5)
manual page.

This feature is available in Postfix 2.0 and later.

Sendmail compatibility feature that specifies the location of the
newaliases(1) command. This command can be used to rebuild the
local(8)aliases(5) database.

The numerical Postfix SMTP server reply code when a client request
is rejected by the reject_non_fqdn_helo_hostname, reject_non_fqdn_sender
or reject_non_fqdn_recipient restriction.

A list of Milter (mail filter) applications for new mail that
does not arrive via the Postfix smtpd(8) server. This includes local
submission via the sendmail(1) command line, new mail that arrives
via the Postfix qmqpd(8) server, and old mail that is re-injected
into the queue with “postsuper -r”. Specify space or comma as a
separator. See the MILTER_README document for details.

This feature is available in Postfix 2.3 and later.

The list of error classes that are reported to the postmaster. These
postmaster notifications do not replace user notifications. The
default is to report only the most serious problems. The paranoid
may wish to turn on the policy (UCE and mail relaying) and protocol
error (broken mail software) reports.

NOTE: postmaster notifications may contain confidential information
such as SASL passwords or message content. It is the system
administrator’s responsibility to treat such information with care.

The error classes are:

bounce (also implies 2bounce)

Send the postmaster copies of the headers of bounced mail, and
send transcripts of SMTP sessions when Postfix rejects mail. The
notification is sent to the address specified with the
bounce_notice_recipient configuration parameter (default: postmaster).

2bounce

Send undeliverable bounced mail to the postmaster. The notification
is sent to the address specified with the 2bounce_notice_recipient
configuration parameter (default: postmaster).

data

Send the postmaster a transcript of the SMTP session with an
error because a critical data file was unavailable. The notification
is sent to the address specified with the error_notice_recipient
configuration parameter (default: postmaster).
This feature
is available in Postfix 2.9 and later.

delay

Send the postmaster copies of the headers of delayed mail (see
delay_warning_time). The
notification is sent to the address specified with the
delay_notice_recipient configuration parameter (default: postmaster).

policy

Send the postmaster a transcript of the SMTP session when a
client request was rejected because of (UCE) policy. The notification
is sent to the address specified with the error_notice_recipient
configuration parameter (default: postmaster).

protocol

Send the postmaster a transcript of the SMTP session in case
of client or server protocol errors. The notification is sent to
the address specified with the error_notice_recipient configuration
parameter (default: postmaster).

resource

Inform the postmaster of mail not delivered due to resource
problems. The notification is sent to the address specified with
the error_notice_recipient configuration parameter (default:
postmaster).

software

Inform the postmaster of mail not delivered due to software
problems. The notification is sent to the address specified with
the error_notice_recipient configuration parameter (default:
postmaster).

Examples:

notify_classes = bounce, delay, policy, protocol, resource, software
notify_classes = 2bounce, resource, software

The location of the OpenSSL command line program openssl(1). This
is used by the “postfix tls” command to create private keys,
certificate signing requests, self-signed certificates, and to
compute public key digests for DANE TLSA records. In multi-instance
environments, this parameter is always determined from the configuration
of the default Postfix instance.

Example:

/etc/postfix/main.cf:
    # NetBSD pkgsrc:
    openssl_path = /usr/pkg/bin/openssl
    # Local build:
    openssl_path = /usr/local/bin/openssl

This feature is available in Postfix 3.1 and later.

Enable special treatment for owner-listname entries in the
aliases(5) file, and don’t split owner-listname and
listname-request address localparts when the recipient_delimiter
is set to “-“. This feature is useful for mailing lists.

A list of Postfix features where the pattern “example.com” also
matches subdomains of example.com,
instead of requiring an explicit “.example.com” pattern. This is
planned backwards compatibility: eventually, all Postfix features
are expected to require explicit “.example.com” style patterns when
you really want to match subdomains.

The following Postfix feature names are supported.

Postfix version 1.0 and later

debug_peer_list,
fast_flush_domains,
mynetworks,
permit_mx_backup_networks,
relay_domains,
transport_maps

Postfix version 1.1 and later

qmqpd_authorized_clients,
smtpd_access_maps,

Postfix version 2.8 and later

postscreen_access_list

Postfix version 3.0 and later

smtpd_client_event_limit_exceptions

Restrict the use of the permit_mx_backup SMTP access feature to
only domains whose primary MX hosts match the listed networks.
The parameter value syntax is the same as with the mynetworks
parameter; note, however, that the default value is empty.

Pattern matching of domain names is controlled by the presence
or absence of “permit_mx_backup_networks” in the
parent_domain_matches_subdomains parameter value.

The name of the pickup(8) service. This service picks up local mail
submissions from the Postfix maildrop queue.

This feature is available in Postfix 2.0 and later.

Optional filter for the pipe(8) delivery agent to change the
delivery status code or explanatory text of successful or unsuccessful
deliveries. See default_delivery_status_filter for details.

This feature is available in Postfix 3.0 and later.

The numerical Postfix SMTP server response code when a request
is rejected by the reject_plaintext_session restriction.

This feature is available in Postfix 2.3 and later.

The name of the postlogd(8) service entry in master.cf.
This service appends logfile records to the file specified
with the maillog_file parameter.

This feature is available in Postfix 3.4 and later.

How much time a postlogd(8) process may take to process a request
before it is terminated by a built-in watchdog timer. This is a
safety mechanism that prevents postlogd(8) from becoming non-responsive
due to a bug in Postfix itself or in system software. This limit
cannot be set under 10s.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 3.4 and later.

The postfix(1) commands that the postmulti(1) instance manager
treats as “control” commands, that operate on running instances. For
these commands, disabled instances are skipped.

This feature is available in Postfix 2.6 and later.

The postfix(1) commands that the postmulti(1) instance manager treats
as “start” commands. For these commands, disabled instances are “checked”
rather than “started”, and failure to “start” a member instance of an
instance group will abort the start-up of later instances.

This feature is available in Postfix 2.6 and later.

The postfix(1) commands that the postmulti(1) instance manager treats
as “stop” commands. For these commands, disabled instances are skipped,
and enabled instances are processed in reverse order.

This feature is available in Postfix 2.6 and later.

Permanent allow/denylist for remote SMTP client IP addresses.
postscreen(8) searches this list immediately after a remote SMTP
client connects. Specify a comma- or whitespace-separated list of
commands (in upper or lower case) or lookup tables. The search stops
upon the first command that fires for the client IP address.

permit_mynetworks

Allowlist the client and
terminate the search if the client IP address matches $mynetworks.
Do not subject the client to any before/after 220 greeting tests.
Pass the connection immediately to a Postfix SMTP server process.

Pattern matching of domain names is controlled by the presence
or absence of “postscreen_access_list” in the
parent_domain_matches_subdomains parameter value.

type:table

Query the specified lookup
table. Each table lookup result is an access list, except that
access lists inside a table cannot specify type:table entries.
To discourage the use of hash, btree, etc. tables, there is no
support for substring matching like smtpd(8). Use CIDR tables
instead.

permit

Allowlist the client and terminate
the search. Do not subject the client to any before/after 220
greeting tests. Pass the connection immediately to a Postfix SMTP
server process.

reject

Denylist the client and terminate
the search. Subject the client to the action configured with the
postscreen_denylist_action configuration parameter.

dunno

All postscreen(8) access lists
implicitly have this command at the end.
When dunno
is executed inside a lookup table, return from the lookup table and
evaluate the next command.
When dunno is executed
outside a lookup table, terminate the search, and subject the client
to the configured before/after 220 greeting tests.

Example:

/etc/postfix/main.cf:
    postscreen_access_list = permit_mynetworks,
        cidr:/etc/postfix/postscreen_access.cidr
    # Postfix < 3.6 use postscreen_blacklist_action.
    postscreen_denylist_action = enforce

/etc/postfix/postscreen_access.cidr:
    # Rules are evaluated in the order as specified.
    # Denylist 192.168.* except 192.168.0.1.
    192.168.0.1         dunno
    192.168.0.0/16      reject

This feature is available in Postfix 2.8.

A list of local postscreen(8) server IP addresses where a
non-allowlisted remote SMTP client can obtain postscreen(8)‘s temporary
allowlist status. This status is required before the client can
talk to a Postfix SMTP server process. By default, a client can
obtain postscreen(8)‘s allowlist status on any local postscreen(8)
server IP address.

When postscreen(8) listens on both primary and backup MX
addresses, the postscreen_allowlist_interfaces parameter can be
configured to give the temporary allowlist status only when a client
connects to a primary MX address. Once a client is allowlisted it
can talk to a Postfix SMTP server on any address. Thus, clients
that connect only to backup MX addresses will never become allowlisted,
and will never be allowed to talk to a Postfix SMTP server process.

Specify a list of network addresses or network/netmask patterns,
separated by commas and/or whitespace. The netmask specifies the
number of bits in the network part of a host address. Continue long
lines by starting the next line with whitespace.

You can also specify “/file/name” or “type:table” patterns. A
“/file/name” pattern is replaced by its contents; a “type:table”
lookup table is matched when a table entry matches a lookup string
(the lookup result is ignored).

The list is matched left to right, and the search stops on the
first match. Specify “!pattern” to exclude an address or network
block from the list.

Note: IP version 6 address information must be specified inside
[] in the postscreen_allowlist_interfaces value, and in files
specified with “/file/name”. IP version 6 addresses contain the
“:” character, and would otherwise be confused with a “type:table”
pattern.

Example:

/etc/postfix/main.cf:
    # Don't allowlist connections to the backup IP address.
    # Postfix < 3.6 use postscreen_whitelist_interfaces.
    postscreen_allowlist_interfaces = !168.100.189.8, static:all

This feature is available in Postfix 3.6 and later.

Available as postscreen_whitelist_interfaces in Postfix 2.9 – 3.5.

The action that postscreen(8) takes when a remote SMTP client sends
a bare newline character, that is, a newline not preceded by carriage
return. Specify one of the following:

ignore

Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects.

This feature is available in Postfix 2.8.

Enable “bare newline” SMTP protocol tests in the postscreen(8)
server. These tests are expensive: a remote SMTP client must
disconnect after
it passes the test, before it can talk to a real Postfix SMTP server.

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will use the result from
a successful “bare newline” SMTP protocol test. During this
time, the client IP address is excluded from this test. The default
is long because a remote SMTP client must disconnect after it passes
the test,
before it can talk to a real Postfix SMTP server.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.8.

Renamed to postscreen_denylist_action in Postfix 3.6.

This feature is available in Postfix 2.8 – 3.5.

The amount of time between postscreen(8) cache cleanup runs.
Cache cleanup increases the load on the cache database and should
therefore not be run frequently. This feature requires that the
cache database supports the “delete” and “sequence” operators.
Specify a zero interval to disable cache cleanup.

After each cache cleanup run, the postscreen(8) daemon logs the
number of entries that were retained and dropped. A cleanup run is
logged as “partial” when the daemon terminates early after “postfix
reload“, “postfix stop“, or no requests for $max_idle
seconds.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

This feature is available in Postfix 2.8.

Persistent storage for the postscreen(8) server decisions.

To share a postscreen(8) cache between multiple postscreen(8)
instances, use “postscreen_cache_map = proxy:btree:/path/to/file”.
This requires Postfix version 2.9 or later; earlier proxymap(8)
implementations don’t support cache cleanup. For an alternative
approach see the memcache_table(5) manpage.

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will cache an expired
temporary allowlist entry before it is removed. This prevents clients
from being logged as “NEW” just because their cache entry expired
an hour ago. It also prevents the cache from filling up with clients
that passed some deep protocol test once and never came back.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.8.

How many simultaneous connections any remote SMTP client is
allowed to have
with the postscreen(8) daemon. By default, this limit is the same
as with the Postfix SMTP server. Note that the triage process can
take several seconds, with the time spent in postscreen_greet_wait
delay, and with the time spent talking to the postscreen(8) built-in
dummy SMTP protocol engine.

This feature is available in Postfix 2.8.

The limit on the total number of commands per SMTP session for
postscreen(8)‘s built-in SMTP protocol engine. This SMTP engine
defers or rejects all attempts to deliver mail, therefore there is
no need to enforce separate limits on the number of junk commands
and error commands.

This feature is available in Postfix 2.8.

A mechanism to transform commands from remote SMTP clients.
See smtpd_command_filter for further details.

This feature is available in Postfix 2.8 and later.

The time limit to read an entire command line with postscreen(8)‘s
built-in SMTP protocol engine.

This feature is available in Postfix 2.8.

The action that postscreen(8) takes when a remote SMTP client is
permanently denylisted with the postscreen_access_list parameter.
Specify one of the following:

ignore (default)

Ignore this result. Allow other tests to complete. Repeat
this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects.

This feature is available in Postfix 3.6 and later.

Available as postscreen_blacklist_action in Postfix 2.8 – 3.5.

Disable the SMTP VRFY command in the postscreen(8) daemon. See
disable_vrfy_command for details.

This feature is available in Postfix 2.8.

Lookup tables, indexed by the remote SMTP client address, with
case insensitive lists of EHLO keywords (pipelining, starttls, auth,
etc.) that the postscreen(8) server will not send in the EHLO response
to a remote SMTP client. See smtpd_discard_ehlo_keywords for details.
The table is not searched by hostname for robustness reasons.

This feature is available in Postfix 2.8 and later.

A case insensitive list of EHLO keywords (pipelining, starttls,
auth, etc.) that the postscreen(8) server will not send in the EHLO
response to a remote SMTP client. See smtpd_discard_ehlo_keywords
for details.

This feature is available in Postfix 2.8 and later.

The action that postscreen(8) takes when a remote SMTP client’s combined
DNSBL score is equal to or greater than a threshold (as defined
with the postscreen_dnsbl_sites and postscreen_dnsbl_threshold
parameters). Specify one of the following:

ignore (default)

Ignore the failure of this test. Allow other tests to complete.
Repeat this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects.

This feature is available in Postfix 2.8.

Allow a remote SMTP client to skip “before” and “after 220
greeting” protocol tests, based on its combined DNSBL score as
defined with the postscreen_dnsbl_sites parameter.

Specify a negative value to enable this feature. When a client
passes the postscreen_dnsbl_allowlist_threshold without having
failed other tests, all pending or disabled tests are flagged as
completed with a time-to-live value equal to postscreen_dnsbl_ttl.
When a test was already completed, its time-to-live value is updated
if it was less than postscreen_dnsbl_ttl.

This feature is available in Postfix 3.6 and later.

Available as postscreen_dnsbl_whitelist_threshold in Postfix 2.11
– 3.5.

The maximum amount of time that postscreen(8) will use the
result from a successful DNS-based reputation test before a
client IP address is required to pass that test again. If the DNS
reply specifies a shorter TTL value, that value will be used unless
it would be smaller than postscreen_dnsbl_min_ttl.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

This feature is available in Postfix 3.1. The default setting
is backwards-compatible with older Postfix versions.

The minimum amount of time that postscreen(8) will use the
result from a successful DNS-based reputation test before a
client IP address is required to pass that test again. If the DNS
reply specifies a larger TTL value, that value will be used unless
it would be larger than postscreen_dnsbl_max_ttl.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 3.1.

A mapping from an actual DNSBL domain name which includes a secret
password, to the DNSBL domain name that postscreen will reply with
when it rejects mail. When no mapping is found, the actual DNSBL
domain will be used.

For maximal stability it is best to use a file that is read
into memory such as pcre:, regexp: or texthash: (texthash: is similar
to hash:, except a) there is no need to run postmap(1) before the
file can be used, and b) texthash: does not detect changes after
the file is read).

Example:

/etc/postfix/main.cf:
    postscreen_dnsbl_reply_map = texthash:/etc/postfix/dnsbl_reply

/etc/postfix/dnsbl_reply:
   secret.zen.spamhaus.org      zen.spamhaus.org

This feature is available in Postfix 2.8.

Optional list of DNS allow/denylist domains, filters and weight
factors. When the list is non-empty, the dnsblog(8) daemon will
query these domains with the IP addresses of remote SMTP clients,
and postscreen(8) will update an SMTP client’s DNSBL score with
each non-error reply.

Caution: when postscreen rejects mail, it replies with the DNSBL
domain name. Use the postscreen_dnsbl_reply_map feature to hide
“password” information in DNSBL domain names.

When a client’s score is equal to or greater than the threshold
specified with postscreen_dnsbl_threshold, postscreen(8) can drop
the connection with the remote SMTP client.

Specify a list of domain=filter*weight entries, separated by
comma or whitespace.

Examples:

To use example.com as a high-confidence blocklist, and to
block mail with example.net and example.org only when both agree:

postscreen_dnsbl_threshold = 2
postscreen_dnsbl_sites = example.com*2, example.net, example.org

To filter only DNSBL replies containing 127.0.0.4:

postscreen_dnsbl_sites = example.com=127.0.0.4

This feature is available in Postfix 2.8.

The inclusive lower bound for blocking a remote SMTP client, based on
its combined DNSBL score as defined with the postscreen_dnsbl_sites
parameter.

This feature is available in Postfix 2.8.

The time limit for DNSBL or DNSWL lookups. This is separate from
the timeouts in the dnsblog(8) daemon which are defined by system
resolver(3) routines.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 3.0.

The amount of time that postscreen(8) will use the result from
a successful DNS-based reputation test before a client
IP address is required to pass that test again.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).

This feature is available in Postfix 2.8-3.0. It was
replaced by postscreen_dnsbl_max_ttl in Postfix 3.1.

Renamed to postscreen_dnsbl_allowlist_threshold in Postfix 3.6.

This feature is available in Postfix 2.11 – 3.5.

Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
require that clients use TLS encryption. See smtpd_postscreen_enforce_tls
for details.

This feature is available in Postfix 2.8 and later.
Preferably, use postscreen_tls_security_level instead.

List of characters that are permitted in postscreen_reject_footer
attribute expansions. See smtpd_expansion_filter for further
details.

This feature is available in Postfix 2.8 and later.

List of commands that the postscreen(8) server considers in
violation of the SMTP protocol. See smtpd_forbidden_commands for
syntax, and postscreen_non_smtp_command_action for possible actions.

This feature is available in Postfix 2.8.

The action that postscreen(8) takes when a remote SMTP client speaks
before its turn within the time specified with the postscreen_greet_wait
parameter. Specify one of the following:

ignore (default)

Ignore the failure of this test. Allow other tests to complete.
Repeat this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects.

In either case, postscreen(8) will not allowlist the remote SMTP client
IP address.

This feature is available in Postfix 2.8.

The text in the optional “220-text…” server
response that
postscreen(8) sends ahead of the real Postfix SMTP server’s “220
text…” response, in an attempt to confuse bad SMTP clients so
that they speak before their turn (pre-greet). Specify an empty
value to disable this feature.

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will use the result from
a successful PREGREET test. During this time, the client IP address
is excluded from this test. The default is relatively short, because
a good client can immediately talk to a real Postfix SMTP server.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will wait for an SMTP
client to send a command before its turn, and for DNS blocklist
lookup results to arrive (default: up to 2 seconds under stress,
up to 6 seconds otherwise).

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.8.

Require that a remote SMTP client sends HELO or EHLO before
commencing a MAIL transaction.

This feature is available in Postfix 2.8.

The action that postscreen(8) takes when a remote SMTP client sends
non-SMTP commands as specified with the postscreen_forbidden_commands
parameter. Specify one of the following:

ignore

Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. This action is the
same as with the Postfix SMTP server’s smtpd_forbidden_commands
feature.

This feature is available in Postfix 2.8.

Enable “non-SMTP command” tests in the postscreen(8) server. These
tests are expensive: a client must disconnect after it passes the
test, before it can talk to a real Postfix SMTP server.

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will use the result from
a successful “non_smtp_command” SMTP protocol test. During this
time, the client IP address is excluded from this test. The default
is long because a client must disconnect after it passes the test,
before it can talk to a real Postfix SMTP server.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.8.

The action that postscreen(8) takes when a remote SMTP client
sends
multiple commands instead of sending one command and waiting for
the server to respond. Specify one of the following:

ignore

Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently.

enforce

Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects.

drop

Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects.

This feature is available in Postfix 2.8.

Enable “pipelining” SMTP protocol tests in the postscreen(8)
server. These tests are expensive: a good client must disconnect
after it passes the test, before it can talk to a real Postfix SMTP
server.

This feature is available in Postfix 2.8.

The amount of time that postscreen(8) will use the result from
a successful “pipelining” SMTP protocol test. During this time, the
client IP address is excluded from this test. The default is
long because a good client must disconnect after it passes the test,
before it can talk to a real Postfix SMTP server.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days).

This feature is available in Postfix 2.8.

The number of clients that can be waiting for service from a
real Postfix SMTP server process. When this queue is full, all
clients will
receive a 421 response.

This feature is available in Postfix 2.8.

The number of non-allowlisted clients that can be waiting for
a decision whether they will receive service from a real Postfix
SMTP server
process. When this queue is full, all non-allowlisted clients will
receive a 421 response.

This feature is available in Postfix 2.8.

Optional information that is appended after a 4XX or 5XX
postscreen(8) server
response. See smtpd_reject_footer for further details.

This feature is available in Postfix 2.8 and later.

Optional lookup table for information that is appended after a 4XX
or 5XX postscreen(8) server response. See smtpd_reject_footer_maps for
further details.

This feature is available in Postfix 3.4 and later.

The SMTP TLS security level for the postscreen(8) server; when
a non-empty value is specified, this overrides the obsolete parameters
postscreen_use_tls and postscreen_enforce_tls. See smtpd_tls_security_level
for details.

This feature is available in Postfix 2.8 and later.

The name of the proxy protocol used by an optional before-postscreen
proxy agent. When a proxy agent is used, this protocol conveys local
and remote address and port information. Specify
“postscreen_upstream_proxy_protocol = haproxy” to enable the haproxy
protocol; version 2 is supported with Postfix 3.5 and later.

This feature is available in Postfix 2.10 and later.

The time limit for the proxy protocol specified with the
postscreen_upstream_proxy_protocol parameter.

This feature is available in Postfix 2.10 and later.

Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
but do not require that clients use TLS encryption.

This feature is available in Postfix 2.8 and later.
Preferably, use postscreen_tls_security_level instead.

How much time a postscreen(8) process may take to respond to
a remote SMTP client command or to perform a cache operation before it
is terminated by a built-in watchdog timer. This is a safety
mechanism that prevents postscreen(8) from becoming non-responsive
due to a bug in Postfix itself or in system software. To avoid
false alarms and unnecessary cache corruption this limit cannot be
set under 10s.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.8.

Renamed to postscreen_allowlist_interfaces in Postfix 3.6.

This feature is available in Postfix 2.9 – 3.5.

The message delivery contexts where the Postfix local(8) delivery
agent prepends a Delivered-To: message header with the address
that the mail was delivered to. This information is used for mail
delivery loop detection.

By default, the Postfix local delivery agent prepends a Delivered-To:
header when forwarding mail and when delivering to file (mailbox)
and command. Turning off the Delivered-To: header when forwarding
mail is not recommended.

Specify zero or more of forward, file, or command.

Example:

prepend_delivered_header = forward

The process ID of a Postfix command or daemon process.

The location of Postfix PID files relative to $queue_directory.
This is a read-only parameter.

The process name of a Postfix command or daemon process.

What address lookup tables copy an address extension from the lookup
key to the lookup result.

For example, with a virtual(5) mapping of “[email protected] =>
[email protected]“, the address “joe [email protected]”
would rewrite to “joe.user [email protected]“.

Specify zero or more of canonical, virtual, alias,
forward, include or generic. These cause
address extension
propagation with canonical(5), virtual(5), and aliases(5) maps,
with local(8) .forward and :include: file lookups, and with smtp(8)
generic maps, respectively.

Note: enabling this feature for types other than canonical
and virtual is likely to cause problems when mail is forwarded
to other sites, especially with mail that is sent to a mailing list
exploder address.

Examples:

propagate_unmatched_extensions = canonical, virtual, alias,
        forward, include
propagate_unmatched_extensions = canonical, virtual

The remote network interface addresses that this mail system receives mail
on by way of a proxy or network address translation unit.

This feature is available in Postfix 2.0 and later.

You must specify your “outside” proxy/NAT addresses when your
system is a backup MX host for other domains, otherwise mail delivery
loops will happen when the primary MX host is down.

Example:

proxy_interfaces = 1.2.3.4

The lookup tables that the proxymap(8) server is allowed to
access for the read-only service.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma.
Table references that don’t begin with proxy: are ignored.

This feature is available in Postfix 2.0 and later.

The lookup tables that the proxymap(8) server is allowed to
access for the read-write service. Postfix-owned local database
files should be stored under the Postfix-owned data_directory.
Table references that don’t begin with proxy: are ignored.

This feature is available in Postfix 2.5 and later.

The name of the proxymap read-only table lookup service. This
service is normally implemented by the proxymap(8) daemon.

This feature is available in Postfix 2.6 and later.

The name of the proxywrite read-write table lookup service.
This service is normally implemented by the proxymap(8) daemon.

This feature is available in Postfix 2.6 and later.

The minimal delay between warnings that a specific destination is
clogging up the Postfix active queue. Specify 0 to disable.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is enabled with the helpful_warnings parameter.

This feature is available in Postfix 2.0 and later.

How much time a Postfix queue manager process may take to handle
a request before it is terminated by a built-in watchdog timer.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.8 and later.

Obsolete feature: the percentage of delivery resources that a busy
mail system will use up for delivery of a large mailing list
message.

This feature exists only in the oqmgr(8) old queue manager. The
current queue manager solves the problem in a better way.

The time limit for the queue manager to send or receive information
over an internal communication channel. The purpose is to break
out of deadlock situations. If the time limit is exceeded the
software either retries or aborts the operation.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

This feature is available in Postfix 2.8 and later.

The maximal number of messages in the active queue.

The maximal number of recipients held in memory by the Postfix
queue manager, and the maximal size of the short-term,
in-memory “dead” destination status cache.

The minimal number of in-memory recipients for any message. This
takes priority over any other in-memory recipient limits (i.e.,
the global qmgr_message_recipient_limit and the per transport
_recipient_limit) if necessary. The minimum value allowed for this
parameter is 1.

What remote QMQP clients are allowed to connect to the Postfix QMQP
server port.

By default, no client is allowed to use the service. This is
because the QMQP server will relay mail to any destination.

Specify a list of client patterns. A list pattern specifies a host
name, a domain name, an internet address, or a network/mask pattern,
where the mask specifies the number of bits in the network part.
When a pattern specifies a file name, its contents are substituted
for the file name; when a pattern is a “type:table” table specification,
table lookup is used instead.

Patterns are separated by whitespace and/or commas. In order to
reverse the result, precede a pattern with an
exclamation point (!). The form “!/file/name” is supported only
in Postfix version 2.4 and later.

Pattern matching of domain names is controlled by the presence
or absence of “qmqpd_authorized_clients” in the
parent_domain_matches_subdomains parameter value.

Example:

qmqpd_authorized_clients = !192.168.0.1, 192.168.0.0/24

Enable logging of the remote QMQP client port in addition to
the hostname and IP address. The logging format is “host[address]:port”.

This feature is available in Postfix 2.5 and later.

How long the Postfix QMQP server will pause before sending a negative
reply to the remote QMQP client. The purpose is to slow down confused
or malicious clients.

Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The time limit for sending or receiving information over the network.
If a read or write operation blocks for more than $qmqpd_timeout
seconds the Postfix QMQP server gives up and disconnects.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The location of the Postfix top-level queue directory. This is the
root directory of Postfix daemon processes that run chrooted.

The maximal number of (name=value) attributes that may be stored
in a Postfix queue file. The limit is enforced by the cleanup(8)
server.

This feature is available in Postfix 2.0 and later.

The minimal amount of free space in bytes in the queue file system
that is needed to receive mail. This is currently used by the
Postfix SMTP server to decide if it will accept any mail at all.

By default, the Postfix SMTP server rejects MAIL FROM commands when
the amount of free space is less than 1.5*$message_size_limit
(Postfix version 2.1 and later).
To specify a higher minimum free space limit, specify a queue_minfree
value that is at least 1.5*$message_size_limit.

With Postfix versions 2.0 and earlier, a queue_minfree value of
zero means there is no minimum required amount of free space.

The time between deferred queue scans by the queue manager;
prior to Postfix 2.4 the default value was 1000s.

This parameter should be set less than or equal to
$minimal_backoff_time. See also $maximal_backoff_time.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The name of the qmgr(8) service. This service manages the Postfix
queue and schedules delivery requests.

This feature is available in Postfix 2.0 and later.

Optional lookup tables with RBL response templates. The tables are
indexed by the RBL domain name. By default, Postfix uses the default
template as specified with the default_rbl_reply configuration
parameter. See there for a discussion of the syntax of RBL reply
templates.

This feature is available in Postfix 2.0 and later.

The location of Postfix README files that describe how to build,
configure or operate a specific Postfix subsystem or feature.

Enable or disable recipient validation, built-in content
filtering, or address mapping. Typically, these are specified in
master.cf as command-line arguments for the smtpd(8), qmqpd(8) or
pickup(8) daemons.

Specify zero or more of the following options. The options
override main.cf settings and are either implemented by smtpd(8),
qmqpd(8), or pickup(8) themselves, or they are forwarded to the
cleanup server.

Do not try to reject unknown recipients (SMTP server only).
This is typically specified AFTER an external content filter.

Disable canonical address mapping, virtual alias map expansion,
address masquerading, and automatic BCC (blind carbon-copy)
recipients. This is typically specified BEFORE an external content
filter.

Disable header/body_checks. This is typically specified AFTER
an external content filter.

Disable Milter (mail filter) applications. This is typically
specified AFTER an external content filter.

Note: when the “BEFORE content filter” receive_override_options
setting is specified in the main.cf file, specify the “AFTER content
filter” receive_override_options setting in master.cf (and vice
versa).

Examples:

receive_override_options =
    no_unknown_recipient_checks, no_header_body_checksreceive_override_options = no_address_mappings

This feature is available in Postfix 2.1 and later.

Optional BCC (blind carbon-copy) address lookup tables, indexed by
recipient address. The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

The table search order is as follows:

Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements RFC 3461.

Note: with Postfix 2.2 and earlier the sender will unconditionally
be notified when the BCC address is undeliverable.

Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself.

Example:

recipient_bcc_maps = hash:/etc/postfix/recipient_bcc

After a change, run “postmap /etc/postfix/recipient_bcc“.

This feature is available in Postfix 2.1 and later.

What addresses are subject to recipient_canonical_maps address
mapping. By default, recipient_canonical_maps address mapping is
applied to envelope recipient addresses, and to header recipient
addresses.

Specify one or more of: envelope_recipient, header_recipient

This feature is available in Postfix 2.2 and later.

Optional address mapping lookup tables for envelope and header
recipient addresses.
The table format and lookups are documented in canonical(5).

Note: $recipient_canonical_maps is processed before $canonical_maps.

Example:

recipient_canonical_maps = hash:/etc/postfix/recipient_canonical

The set of characters that can separate an email address
localpart, user name, or a .forward file name from its extension.
For example, with “recipient_delimiter = “, the software tries
user [email protected] before trying [email protected], user foo before
trying user, and .forward foo before trying .forward.

More formally, an email address localpart or user name is
separated from its extension by the first character that matches
the recipient_delimiter set. The delimiter character and extension
may then be used to generate an extended .forward file name. This
implementation recognizes one delimiter character and one extension
per email address localpart or email address. With Postfix 2.10 and
earlier, the recipient_delimiter specifies a single character.

See canonical(5), local(8), relocated(5) and virtual(5) for the
effects of recipient_delimiter on lookups in aliases, canonical,
virtual, and relocated maps, and see the propagate_unmatched_extensions
parameter for propagating an extension from one email address to
another.

When used in command_execution_directory, forward_path, or
luser_relay, ${recipient_delimiter} is replaced with the actual
recipient delimiter that was found in the recipient email address
(Postfix 2.11 and later), or it is replaced with the main.cfrecipient_delimiter parameter value (Postfix 2.10 and earlier).

The recipient_delimiter is not applied to the mailer-daemon
address, the postmaster address, or the double-bounce address. With
the default “owner_request_special = yes” setting, the recipient_delimiter
is also not applied to addresses with the special “owner-” prefix
or the special “-request” suffix.

Examples:

# Handle Postfix-style extensions.
recipient_delimiter =  

# Handle both Postfix and qmail extensions (Postfix 2.11 and later).
recipient_delimiter =  -

# Use .forward for mail without address extension, and for mail with
# an unrecognized address extension.
forward_path = $home/.forward${recipient_delimiter}${extension},
    $home/.forward

The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the “reject” restriction.

Do not change this unless you have a complete understanding of RFC 5321.

The Postfix SMTP server’s action when a reject-type restriction
fails due to a temporary error condition. Specify “defer” to defer
the remote SMTP client request immediately. With the default
“defer_if_permit” action, the Postfix SMTP server continues to look
for opportunities to reject mail, and defers the client request
only if it would otherwise be accepted.

For finer control, see: unverified_recipient_tempfail_action,
unverified_sender_tempfail_action, unknown_address_tempfail_action,
and unknown_helo_hostname_tempfail_action.

This feature is available in Postfix 2.6 and later.

List of tables with remote SMTP client-certificate fingerprints or
public key fingerprints (Postfix 2.9 and later) for which the Postfix
SMTP server will allow access with the permit_tls_clientcerts
feature. The fingerprint digest algorithm is configurable via the
smtpd_tls_fingerprint_digest parameter (hard-coded as md5 prior to
Postfix version 2.5).

The default algorithm is sha256 with Postfix ≥ 3.6
and the compatibility_level set to 3.6 or higher. With Postfix
≤ 3.5, the default algorithm is md5. The best-practice
algorithm is now sha256. Recent advances in hash function
cryptanalysis have led to md5 and sha1 being deprecated in favor of
sha256. However, as long as there are no known “second pre-image”
attacks against the older algorithms, their use in this context, though
not recommended, is still likely safe.

Postfix lookup tables are in the form of (key, value) pairs.
Since we only need the key, the value can be chosen freely, e.g.
the name of the user or host:
D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home

Example:

relay_clientcerts = hash:/etc/postfix/relay_clientcerts

For more fine-grained control, use check_ccert_access to select
an appropriate access(5) policy for each client.
See RESTRICTION_CLASS_README.

This feature is available with Postfix version 2.2.

The maximal number of parallel deliveries to the same destination
via the relay message delivery transport. This limit is enforced
by the queue manager. The message delivery transport name is the
first field in the entry in the master.cf file.

This feature is available in Postfix 2.0 and later.

The maximal number of recipients per message for the relay
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the master.cf file.

Setting this parameter to a value of 1 changes the meaning of
relay_destination_concurrency_limit from concurrency per domain
into concurrency per recipient.

This feature is available in Postfix 2.0 and later.

What destination domains (and subdomains thereof) this system
will relay mail to. For details about how
the relay_domains value is used, see the description of the
permit_auth_destination and reject_unauth_destination SMTP recipient
restrictions.

Domains that match $relay_domains are delivered with the
$relay_transport mail delivery transport. The SMTP server validates
recipient addresses with $relay_recipient_maps and rejects non-existent
recipients. See also the relay domains address class in the
ADDRESS_CLASS_README file.

Note: Postfix will not automatically forward mail for domains
that list this system as their primary or backup MX host. See the
permit_mx_backup restriction in the postconf(5) manual page.

Specify a list of host or domain names, “/file/name” patterns
or “type:table” lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
“/file/name” pattern is replaced by its contents; a “type:table”
lookup table is matched when a (parent) domain appears as lookup
key. Specify “!pattern” to exclude a domain from the list. The form
“!/file/name” is supported only in Postfix version 2.4 and later.

Pattern matching of domain names is controlled by the presence
or absence of “relay_domains” in the parent_domain_matches_subdomains
parameter value.

The numerical Postfix SMTP server response code when a client
request is rejected by the reject_unauth_destination recipient
restriction.

Do not change this unless you have a complete understanding of RFC 5321.

Optional lookup tables with all valid addresses in the domains
that match $relay_domains. Specify @domain as a wild-card for
domains that have no valid recipient list, and become a source of
backscatter mail: Postfix accepts spam for non-existent recipients
and then floods innocent people with undeliverable mail. Technically,
tables
listed with $relay_recipient_maps are used as lists: Postfix needs
to know only if a lookup string is found or not, but it does not
use the result from the table lookup.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

If this parameter is non-empty, then the Postfix SMTP server will reject
mail to unknown relay users. This feature is off by default.

See also the relay domains address class in the ADDRESS_CLASS_README
file.

Example:

relay_recipient_maps = hash:/etc/postfix/relay_recipients

This feature is available in Postfix 2.0 and later.

The default mail delivery transport and next-hop destination for
remote delivery to domains listed with $relay_domains. In order of
decreasing precedence, the nexthop destination is taken from
$relay_transport, $sender_dependent_relayhost_maps, $relayhost, or
from the recipient domain. This information can be overruled with
the transport(5) table.

Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in master.cf.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent.

See also the relay domains address class in the ADDRESS_CLASS_README
file.

This feature is available in Postfix 2.0 and later.

The next-hop destination(s) for non-local mail; overrides non-local
domains in recipient addresses. This information is overruled with
relay_transport, sender_dependent_default_transport_maps,
default_transport, sender_dependent_relayhost_maps
and with the transport(5) table.

On an intranet, specify the organizational domain name. If your
internal DNS uses no MX records, specify the name of the intranet
gateway host instead.

In the case of SMTP or LMTP delivery, specify one or more destinations
in the form of a domain name, hostname, hostname:port, [hostname]:port,
[hostaddress] or [hostaddress]:port, separated by comma or whitespace.
The form [hostname] turns off MX lookups. Multiple destinations are
supported in Postfix 3.5 and later.

If you’re connected via UUCP, see the UUCP_README file for useful
information.

Examples:

relayhost = $mydomainrelayhost = [gateway.example.com]
relayhost = mail1.example:587, mail2.example:587
relayhost = [an.ip.add.ress]

Optional lookup tables with new contact information for users or
domains that no longer exist. The table format and lookups are
documented in relocated(5).

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

If you use this feature, run “postmap /etc/postfix/relocated” to
build the necessary DBM or DB file after change, then “postfix
reload” to make the changes visible.

Examples:

relocated_maps = dbm:/etc/postfix/relocated
relocated_maps = hash:/etc/postfix/relocated

Don’t rewrite message headers from remote clients at all when
this parameter is empty; otherwise, rewrite message headers and
append the specified domain name to incomplete addresses. The
local_header_rewrite_clients parameter controls what clients Postfix
considers local.

Examples:

The safe setting: append “domain.invalid” to incomplete header
addresses from remote SMTP clients, so that those addresses cannot
be confused with local addresses.

remote_header_rewrite_domain = domain.invalid

The default, purist, setting: don’t rewrite headers from remote
clients at all.

remote_header_rewrite_domain =

Require that a local(8) recipient’s home directory exists
before mail delivery is attempted. By default this test is disabled.
It can be useful for environments that import home directories to
the mail server (IMPORTING HOME DIRECTORIES IS NOT RECOMMENDED).

Reset the local(8) delivery agent’s idea of the owner-alias
attribute, when delivering mail to a child alias that does not have
its own owner alias.

This feature is available in Postfix 2.8 and later. With older
Postfix releases, the behavior is as if this parameter is set to
“yes”.

As documented in aliases(5), when an alias name has a
companion alias named owner-name, this will replace the
envelope sender address, so that delivery errors will be
reported to the owner alias instead of the sender. This configuration
is recommended for mailing lists.

A less known property of the owner alias is that it also forces
the local(8) delivery agent to write local and remote addresses
from alias expansion to a new queue file, instead of attempting to
deliver mail to local addresses as soon as they come out of alias
expansion.

Writing local addresses from alias expansion to a new queue
file allows for robust handling of temporary delivery errors: errors
with one local member have no effect on deliveries to other members
of the list. On the other hand, delivery to local addresses as
soon as they come out of alias expansion is fragile: a temporary
error with one local address from alias expansion will cause the
entire alias to be expanded repeatedly until the error goes away,
or until the message expires in the queue. In that case, a problem
with one list member results in multiple message deliveries to other
list members.

The default behavior of Postfix 2.8 and later is to keep the
owner-alias attribute of the parent alias, when delivering mail to
a child alias that does not have its own owner alias. Then, local
addresses from that child alias will be written to a new queue file,
and a temporary error with one local address will not affect delivery
to other mailing list members.

Unfortunately, older Postfix releases reset the owner-alias
attribute when delivering mail to a child alias that does not have
its own owner alias. To be precise, this resets only the decision
to create a new queue file, not the decision to override the envelope
sender address. The local(8) delivery agent then attempts to
deliver local addresses as soon as they come out of child alias
expansion. If delivery to any address from child alias expansion
fails with a temporary error condition, the entire mailing list may
be expanded repeatedly until the mail expires in the queue, resulting
in multiple deliveries of the same message to mailing list members.

Resolve a recipient address safely instead of correctly, by
looking inside quotes.

By default, the Postfix address resolver does not quote the
address localpart as per RFC 822, so that additional @ or % or !
operators remain visible. This behavior is safe but it is also
technically incorrect.

If you specify “resolve_dequoted_address = no”, then
the Postfix
resolver will not know about additional @ etc. operators in the
address localpart. This opens opportunities for obscure mail relay
attacks with user@domain@domain addresses when Postfix provides
backup MX service for Sendmail systems.

Resolve an address that ends in the “@” null domain as if the
local hostname were specified, instead of rejecting the address as
invalid.

This feature is available in Postfix 2.1 and later.
Earlier versions always resolve the null domain as the local
hostname.

The Postfix SMTP server uses this feature to reject mail from
or to addresses that end in the “@” null domain, and from addresses
that rewrite into a form that ends in the “@” null domain.

Resolve “user@ipaddress” as “user@[ipaddress]”, instead of
rejecting the address as invalid.

This feature is available in Postfix 2.3 and later.

Avoid logging that implies white is better than black. Instead
use ‘allowlist’, ‘denylist’, and variations of those words.

This feature is available in Postfix 3.6 and later.

The name of the address rewriting service. This service rewrites
addresses to standard form and resolves them to a (delivery method,
next-hop host, recipient) triple.

This feature is available in Postfix 2.0 and later.

The name of the directory with example Postfix configuration files.
Starting with Postfix 2.1, these files have been replaced with the
postconf(5) manual page.

When authenticating to a remote SMTP or LMTP server with the
default setting “no”, send no SASL authoriZation ID (authzid); send
only the SASL authentiCation ID (authcid) plus the authcid’s password.

The non-default setting “yes” enables the behavior of older
Postfix versions. These always send a SASL authzid that is equal
to the SASL authcid, but this causes interoperability problems
with some SMTP servers.

This feature is available in Postfix 2.4.4 and later.

This parameter should not be used. It was replaced by sender_dependent_relayhost_maps
in Postfix version 2.3.

Optional BCC (blind carbon-copy) address lookup tables, indexed
by sender address. The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

The table search order is as follows:

Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements RFC 3461.

Note: with Postfix 2.2 and earlier the sender will be notified
when the BCC address is undeliverable.

Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself.

Example:

sender_bcc_maps = hash:/etc/postfix/sender_bcc

After a change, run “postmap /etc/postfix/sender_bcc“.

This feature is available in Postfix 2.1 and later.

What addresses are subject to sender_canonical_maps address
mapping. By default, sender_canonical_maps address mapping is
applied to envelope sender addresses, and to header sender addresses.

Specify one or more of: envelope_sender, header_sender

This feature is available in Postfix 2.2 and later.

Optional address mapping lookup tables for envelope and header
sender addresses.
The table format and lookups are documented in canonical(5).

Example: you want to rewrite the SENDER address “[email protected]”
to “[email protected]”, while still being able to send mail to
the RECIPIENT address “[email protected]”.

Note: $sender_canonical_maps is processed before $canonical_maps.

Example:

sender_canonical_maps = hash:/etc/postfix/sender_canonical

A sender-dependent override for the global default_transport
parameter setting. The tables are searched by the envelope sender
address and @domain. A lookup result of DUNNO terminates the search
without overriding the global default_transport parameter setting.
This information is overruled with the transport(5) table.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

Note: this overrides default_transport, not transport_maps, and
therefore the expected syntax is that of default_transport, not the
syntax of transport_maps. Specifically, this does not support the
transport_maps syntax for null transport, null nexthop, or null
email addresses.

For safety reasons, this feature does not allow $number
substitutions in regular expression maps.

This feature is available in Postfix 2.7 and later.

A sender-dependent override for the global relayhost parameter
setting. The tables are searched by the envelope sender address and
@domain. A lookup result of DUNNO terminates the search without
overriding the global relayhost parameter setting (Postfix 2.6 and
later). This information is overruled with relay_transport,
sender_dependent_default_transport_maps, default_transport and with
the transport(5) table.

Specify zero or more “type:name” lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.

For safety reasons, this feature does not allow $number
substitutions in regular expression maps.

This feature is available in Postfix 2.3 and later.

Controls how the Postfix sendmail command converts email message
line endings from <CR><LF> into UNIX format (<LF>).

always

Always convert message lines ending
in <CR><LF>. This setting is the default with Postfix
2.9 and later.

strict

Convert message lines ending in
<CR><LF> only if the first input line ends in
<CR><LF>. This setting is backwards-compatible with
Postfix 2.8 and earlier.

never

Never convert message lines ending in
<CR><LF>. This setting exists for completeness only.

This feature is available in Postfix 2.9 and later.

A Sendmail compatibility feature that specifies the location of
the Postfix sendmail(1) command. This command can be used to
submit mail into the Postfix queue.

The master.cf service name of a Postfix daemon process. This
can be used to distinguish the logging from different services that
use the same program name.

Example master.cf entries:

# Distinguish inbound MTA logging from submission and smtps logging.
smtp      inet  n       -       n       -       -       smtpd
submission inet n       -       n       -       -       smtpd
    -o syslog_name=postfix/$service_name
smtps     inet  n       -       n       -       -       smtpd
    -o syslog_name=postfix/$service_name

# Distinguish outbound MTA logging from inbound relay logging.
smtp      unix  -       -       n       -       -       smtp
relay     unix  -       -       n       -       -       smtp
    -o syslog_name=postfix/$service_name

How long the Postfix master(8) waits before forking a server that
appears to be malfunctioning.

Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).

The group ownership of set-gid Postfix commands and of group-writable
Postfix directories. When this parameter value is changed you need
to re-run “postfix set-permissions” (with Postfix version 2.0 and
earlier: “/etc/postfix/post-install set-permissions“.

The location of Postfix dynamically-linked libraries
(libpostfix-*.so), and the default location of Postfix database
plugins (postfix-*.so) that have a relative pathname in the
dynamicmaps.cf file. The shlib_directory parameter defaults to
“no” when Postfix dynamically-linked libraries and database plugins
are disabled at compile time, otherwise it typically defaults to
/usr/lib/postfix or /usr/local/lib/postfix.

Notes:

This feature is available in Postfix 3.0 and later.

Display the name of the recipient table in the “User unknown”
responses. The extra detail makes troubleshooting easier but also
reveals information that is nobody else’s business.

This feature is available in Postfix 2.0 and later.

The name of the showq(8) service. This service produces mail queue
status reports.

This feature is available in Postfix 2.0 and later.

The address type (“ipv6”, “ipv4” or “any”) that the Postfix
SMTP client will try first, when a destination has IPv6 and IPv4
addresses with equal MX preference. This feature has no effect
unless the inet_protocols setting enables both IPv4 and IPv6.

Postfix SMTP client address preference has evolved. With Postfix
2.8 the default is “ipv6”; earlier implementations are hard-coded
to prefer IPv6 over IPv4.

Notes for mail delivery between sites that have both IPv4 and
IPv6 connectivity:

This feature is available in Postfix 2.8 and later.

In the context of email address verification, the SMTP protocol
stage that determines whether an email address is deliverable.
Specify one of “rcpt” or “data”. The latter is needed with remote
SMTP servers that reject recipients after the DATA command. Use
transport_maps to apply this feature selectively:

/etc/postfix/main.cf:
    transport_maps = hash:/etc/postfix/transport

/etc/postfix/transport:
    smtp-domain-that-verifies-after-data    smtp-data-target:
    lmtp-domain-that-verifies-after-data    lmtp-data-target:

/etc/postfix/master.cf:
    smtp-data-target    unix    -    -    n    -    -    smtp
        -o smtp_address_verify_target=data
    lmtp-data-target    unix    -    -    n    -    -    lmtp
        -o lmtp_address_verify_target=data

Unselective use of the “data” target does no harm, but will
result in unnecessary “lost connection after DATA” events at remote
SMTP/LMTP servers.

This feature is available in Postfix 3.0 and later.

Always send EHLO at the start of an SMTP session.

With “smtp_always_send_ehlo = no”, the Postfix SMTP client sends
EHLO only when
the word “ESMTP” appears in the server greeting banner (example:
220 spike.porcupine.org ESMTP Postfix).

When a remote destination resolves to a combination of IPv4 and
IPv6 addresses, ensure that the Postfix SMTP client can try both
address types before it runs into the smtp_mx_address_limit.

This avoids an interoperability problem when a destination resolves
to primarily IPv6 addresses, the smtp_address_limit feature eliminates
most or all IPv4 addresses, and the destination is not reachable over
IPv6.

This feature is available in Postfix 3.3 and later.

An optional numerical network address that the Postfix SMTP client
should bind to when making an IPv4 connection.

This can be specified in the main.cf file for all SMTP clients, or
it can be specified in the master.cf file for a specific client,
for example:

/etc/postfix/master.cf:
    smtp ... smtp -o smtp_bind_address=11.22.33.44

See smtp_bind_address_enforce for how Postfix should handle
errors (Postfix 3.7 and later).

Note 1: when inet_interfaces specifies no more than one IPv4
address, and that address is a non-loopback address, it is
automatically used as the smtp_bind_address. This supports virtual
IP hosting, but can be a problem on multi-homed firewalls. See the
inet_interfaces documentation for more detail.

Note 2: address information may be enclosed inside [],
but this form is not required here.